Psoriasis: Symptoms, Types, Causes, Treatments and Pictures

What is Psoriasis?

Psoriasis is a noncontagious, chronic skin condition in which keratocytes (skin cells) are produced and differentiated at a faster than normal rate, resulting in thickening of the epidermal layers, with increased keratinization and peeling.

The exact cause and mechanism of psoriasis has not yet been pin-pointed, but an underlying cause of psoriasis is overactive T lymphocytes that trigger an autoimmune response in the skin, which contributes to the signs and symptoms of inflammation, pain, redness, irritation, and presence of silver scales on the skin. The symptoms of psoriasis can come and go in cycles, with periods of flare-ups usually triggered by external stresses.

Anyone has the potential to develop psoriasis, and is not limited to a specific age, sex, race, location, etc. However, some risk factors that contribute to the manifestation of psoriasis in a certain person are: family history, current health status, lifestyle, and the environment they live in. Psoriasis is not considered physically disabling, but there may be times when the itchiness and pain can prevent a person from doing activities they normally would. Though psoriasis does not cause any crippling physical or mental defects, their appearance to other people may cause psychological problems and people suffering from psoriasis may develop feelings of self-consciousness, which may cause them to opt out of social interactions, and potentially lead to anti-social behavior and depression. Much of the negative social image toward people with psoriasis stems from lack of understanding of the condition.

Currently, there is no known cure for psoriasis, however those afflicted with this condition can find relief of their symptoms through various lifestyle changes and medications, both topical and systemic. Determination and avoidance of specific flare-up triggers is also an effective strategy used to minimize the effects of psoriasis. It is also possible for a patient’s psoriasis to subside for a length of time after a flare-up, or even go into complete remission.

Signs and Symptoms of Psoriasis

Generally, the signs and symptoms of psoriasis are the same in every case, only differing in the level of severity and the type of rashes. Because there are no diagnostic laboratory tests to confirm if a person has or is carrying psoriasis, physicians can only use a patient’s signs and symptoms to diagnose them with psoriasis. As an overview, a sign is what can be seen and quantified by a physician, such as: temperature, localized redness, and presence of skin lesions, while a symptom is a qualitative measurement given by the patient, such as: lethargy, itchiness, and headache. There are actually five different forms of psoriasis, each of which carry their own characteristic rash patterning and distribution. This will be discussed in further detail under the next section: types of psoriasis.

General signs of psoriasis include: red patches of skin, appearance of silver-colored scales, dry and cracked skin, thickened or pitted nails. General symptoms of psoriasis include: swollen and stiff joints; itching, burning, or soreness of the skin, that may come and go after weeks or months.

If you suspect that you have psoriasis, it is important to consult a doctor for an initial physical exam and history taking, because there are several conditions that can be mistaken for psoriasis. Some diseases and conditions that may mimic or occur simultaneously with psoriasis include: lichen planus, pityriasis rosea, seborrheic dermatitis, and tinea corporis. Below are the signs and symptoms of these conditions which can be differentiated from psoriasis:

Lichen planus is a skin condition that is characterized as the appearance of inflamed, itchy, flat-topped lesions arranged in rows that are localized on the arms and legs. Pityriasis rosea, meaning “fine pink scale”, is a common and self-limiting skin condition which is characterized by the initial appearance of a large spot on the abdomen, chest, or back, which then spreads in a Christmas tree-like pattern. Seborrheic dermatitis is an inflammation of the skin, characterized by red, oily, itchy, and scaly skin. It is localized on the face, upper chest, back, and/or scalp. When it occurs on the scalp, it can produce dandruff. Tinea corporis, commonly known as ringworm of the body, is a fungal infection that can cause redness, scaling, and itchiness, in a characteristic ring shape on the top layer of the skin.

Psoriasis Pictures

Psoriasis of the palms

Back and arms of a person with psoriasis
Image credit to James Heilman, MD

The Types of Psoriasis

Although not known to most people, psoriasis has five different subtypes which can be distinguished by the characteristics and location of the rashes that appear on the skin of the person with the condition. A person may actually have one or more different subtypes of psoriasis at a given time, on different areas of the body. The level of severity of psoriasis can also range from mild to moderate to severe. It is important to know the characteristics of the different types of psoriasis, for your doctor to properly diagnose and treat the disease. Listed below are the five different types of psoriasis, according to the United States’ National Psoriasis Foundation:

Plaque Psoriasis

This is the most common form of psoriasis. It appears as raised, patches (plaques) that are red at the base and covered with a silvery-white buildup of dead skin cells. The plaques are often itchy and painful, and they can crack and bleed, especially when scratched. Plaque psoriasis can occur on any part of the body, but is frequently found on the scalp, knees, elbows and lower back. Occasionally, it can be found in the genital area or the soft tissue inside of the mouth.

Psoriatic plaque
Psoriatic plaque, Image credit to James Heilman, MD

Guttate Psoriasis

This is the second most common form of psoriasis, occurring in about ten percent of people with psoriasis. This type of psoriasis often occurs during early or late adolescence, and can be triggered by a streptococcal infection, particularly strep throat. Its rashes are characterized as small, water droplet-like blisters covered in fine scales which do not thicken as much as plaque. These rashes can typically be found on the abdomen, chest, back, upper and lower extremities, and scalp. Guttate psoriasis may occur once then go into remission, or may come back in repeated cycles.

Psoriasis guttata

Inverse Psoriasis

This type of psoriasis shows up as vibrant, red lesions in skin folds, such as behind the knee, under the arm, or in the groin area. In overweight and obese individuals, there is an increase in the amount of skin folds where inverse psoriasis may occur. As compared to the plaque and guttate forms psoriasis, inverse psoriasis is characterized by flat, smooth patches of skin rashes. Triggers for this type of psoriasis are friction, sweating, and fungal infections. It is common for some people to have another type of psoriasis elsewhere on the body, at the same time.
Inverse Psoriasis

Pustular Psoriasis

Pustular psoriasis is an uncommon form of psoriasis. It is characterized by white pustules (blisters) surrounded by red skin. The blisters develop quickly, usually within hours after the appearance of redness on the skin. The pus consists of white blood cells, but it is not caused by an infection, nor is it contagious. The white blood cells in the pus are a consequence of the hyperactivity of the T lymphocytes attacking the skin cells. Pustular psoriasis can occur on any part of the body (generalized pustular psoriasis), but occurs most often on the hands, fingers, or feet. The generalized type of pustular psoriasis can come and go frequently, and carries with it symptoms of chills, fever, excessive itchiness, and diarrhea; these symptoms are likely related to the amount of white blood cells that are attracted to the area.

Severe pustular psoriasis or Psoriasis manum
Severe pustular psoriasis image credit: George Henry Fox

Erythrodermic Psoriasis

Erythrodermic psoriasis is the rarest form of psoriasis, occurring in only about three percent of people with psoriasis. It is a particularly severe form of psoriasis that leads to widespread, vibrant redness over most of the body. It can cause severe itching and burning pain, and makes the skin peel off in sheets. It generally occurs in people who have unstable plaque psoriasis.

Psoriatic Arthritis

Of the people who develop psoriasis, approximately fifteen to thirty percent will also develop another disease known as psoriatic arthritis. There is also a possibility of developing psoriatic arthritis without currently having psoriasis, but the two are usually associated and heavily influenced by hereditary factors.

Like psoriasis of the skin, psoriasis of the joints is caused by hyperactivity of the T lymphocytes, but in addition to and/or instead of affecting the keratinocytes of the skin, the T lymphocytes are directed toward the chondrocytes (cells that make up the cartilage of joints). This results in inflammation and pain in the area.

As in rheumatic arthritis, it presents itself as pain in the joints upon movement, and can be quite debilitating while trying to perform daily activities. The pain may be treated effectively, but the disease should be identified as early as possible, in order to avoid premature and irreversible degradation of the joints. This irreversible degradation is due to the nature of the joints in comparison to the skin. In the skin, the epithelium is normally renewed at a relatively quick and frequent rate. In psoriasis of the skin, this is sped up to almost twice the speed resulting in excess skin cells. In the joints, cartilage contains no blood vessels and therefore does not receive as much nutrients as tissues and organs like the skin. When there is injury to this area, it will not be able to regenerate properly, thus thinning of the available cartilage. The thinning of cartilage makes these areas weaker, and susceptible to wear and tear with frequent movement. Once the cartilage is worn down, there will be no cushion between the bones, resulting in pain and alteration in the range of motion of the joint. With T lymphocytes triggering an inflammatory response in the joint area, this will also cause pain and swelling in the joint space.

There are theories that suggest a person with the “right” genetic background can develop psoriatic arthritis after being exposed to an infection, which triggers the initial response of the T lymphocytes, but for some reason the lymphocytes become hyperreactive and eventually becomes an autoimmune response.

What Causes Psoriasis?

The rashes, irritation, and other effects of psoriasis are due to the body’s immune response to its own cells, which results in the release of inflammatory molecules and accelerated cell proliferation, particularly that of the skin.  However, as stated previously, the exact cause of this autoimmune response is unknown, but research and studies have shown that genetics and the immune system play a significant role in the manifestation of psoriasis.

For a more in-depth understanding of what happens to a person who develops psoriasis, one must understand the skin, the immune system, and genetics:

Role of the Skin in Psoriasis

The skin is considered the body’s largest organ, and one of the first lines of defense against foreign invaders from the outside environment. The majority of the skin of the body consists of four (4) epidermal layers (strata) consisting of keratinocytes, namely: stratum basale (basal layer), stratum spinosum (spinous layer), stratum granulosum (granular layer), and stratum corneum (keratinized layer). In the basal layer, the cells normally undergo mitosis (cell division) and the entire epithelial layer is renewed every fifteen to thirty days. However, when a person has psoriasis, the mitotic activity of the basal stem cells of the keratinocytes is sped up and may take as little as eight days. This causes a build-up of dead keratinocytes, resulting in thickening of the skin and increased flaking.

Role of the Immune System in Psoriasis

The immune system provides a way for the body to defend itself against foreign invaders and potentially harmful cells and materials produced within the body. Its job is to also maintain the body’s homeostasis by constantly checking its own cells for any defects and mutations, and properly eliminating them before those cells can proliferate and cause harm.

The cells that mediate this response are generally called leukocytes, or white blood cells, which are constantly circulating in the bloodstream. There are several types of white blood cells, namely: basophils, eosinophils, neutrophils, monocytes, and lymphocytes. The lymphocytes are the key players of the body’s immune system due to their ability to recognize antigens and can be divided into either T cells or B cells. B cells generally produce antibodies as a response to an antigen presented to it, which is important in long-term immunity. T cells function by recognizing receptors on various cells and releasing cytokines and can be further subdivided into helper T cells, and cytotoxic or “killer” T cells. Cytokines are used as cell-signaling molecules which attract nearby cells such as macrophages and other lymphocytes to aggregate in an area in response to foreign invaders. In turn these cells release more cytokines and other metabolically active substances.

All cells from tissues in the body present certain proteins on their surface called the major histocompatibility complex (MHC), which is used by the body to identify “self” from “non-self” substances. MHCs present itself to T cells and under normal circumstances, elicits no immune response. In the case of psoriasis, by unknown causes, the T cells react with these normal cells in the skin and elicits an immune response, causing a need for the skin cells to divide more quickly and react as if it were under attack by a foreign infection. Some of these response mechanisms include local vasodilation, redness, inflammation, which in turn may also cause pain, and pus-formation due to the subsequent death of the white blood cells.

Role of Genetics in Psoriasis

A person’s genetics determines everything in their body from the color of their skin, eyes, and hair, to their height, and even to the diseases and conditions they will likely develop in their lifetime. Unlike diseases and conditions that develop due to environmental exposure and lifestyle, those that are determined by genetics have little chance of being prevented and modified, except through genetic therapy.

Scientists have currently uncovered about twenty-five genetic variations that contribute to psoriasis, but there is no single “psoriasis-carrying” gene. With that, there is a greater chance of developing psoriasis when one or both parents have psoriasis. However, since psoriasis is not carried by any single gene, the disease is not simply inherited as would blood type or eye color. The gene does not seem to be sex-linked, because psoriasis affects both females and males in equal numbers. People who have psoriasis tend to become predisposed to other diseases and conditions such as cardiovascular disease, arthritis, and diabetes.

There seems to be no specific genes that cause psoriasis which are linked to any particular race, because psoriasis is found in all races and regions of the world. However, research shows that there are more numerous cases of psoriasis affecting people of Caucasian background than people of African-descent. This may be attributed to the location and environment of these groups of people rather than race itself, as it has been said that colder climates and less exposure to sunlight can be triggers for psoriasis. Typically, people of Caucasian background are generally located in Europe and North America, where the climate is generally colder with longer winters, which vastly differs from that of Africa and other continents and countries that are situated along the Equator where there are longer daylight hours and warmer temperatures all year round.

A person who carries the genetic makeup necessary to develop psoriasis may not immediately manifest the signs and symptoms of the condition. Usually, the first manifestation of psoriasis is associated with an initial exposure to a triggering factor (see the triggers section, below). This can occur in adolescence or later in adulthood. There is no age-limit as to when psoriasis will emerge in a person, but certain types of psoriasis is more common in adolescence while others are more common in adults. Psoriatic arthritis tends to emerge in people aged thirty to fifty.

Triggers and Risk Factors

Triggers

Often times, a person with psoriasis will have specific triggers that will elicit an autoimmune response and cause a flare-up of their condition. Though it can vary widely from person to person, some common triggers include: certain medications, infection, injury to the skin, stress, smoking, and the weather. Keep in mind that triggers are not the synonymous with causes of psoriasis, as the cause is inherent to genetics. They are simply the spark that sets off the genetic time bomb that is psoriasis.

Food, Drug, and Disease Interactions of Psoriasis

    1. Does alcohol cause psoriasis flare ups?
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    3. Does Aspartame interact with Psoriasis?
    4. Do allergy medicines cause psoriasis?
    5. Can antidepressants such as amitriptyline cause psoriasis?
    6. Can high uric acid cause psoriasis?
    7. Link between gout and psoriasis
    8. Can beta blockers cause psoriasis?
    9. Can amoxicillin cause psoriasis?
    10. Can Arava medicine cause psoriasis?
    11. Asthma and psoriasis link
    12. Can birth control pills cause psoriasis?
    13. Can botox cause dry skin pr psoriasis?
    14. Does adderall cause psoriasis?
    15. Is biotin good for psoriasis?
    16. Can azathioprine cause psoriasis?
    17. Can advil cause psoriasis?
    18. Can ambien cause psoriasis?
    19. Can adrenal fatigue cause psoriasis?

Risk Factors

As mentioned previously, family history of psoriasis is a major risk factor due to genetic predisposition. Sex and age are not considered major risk factors, although certain types of psoriasis tend to be more common in onset for certain age groups. People with psoriasis may have a slightly higher chance of developing cardiovascular disease, diabetes, obesity, and asthma.

People with psoriasis have a greater chance of developing cardiovascular diseases, because of the increased risk of atherosclerosis, which occurs when plaque builds-up on the walls of blood vessels, increasing blood pressure and the chance of embolism production. Those with severe psoriasis are twice as likely to develop diabetes mellitus than those without psoriasis. Type 2 diabetes and cardiovascular disease are generally linked together, because of the increased likelihood of a person being overweight and having a sedentary lifestyle. According to a study published by the British Association of Dermatologists, those with psoriasis were about forty percent more likely to develop asthma, than those without psoriasis. The underlying cause has not been determined, but it is suggested that the chronic inflammatory nature of both conditions is linked to genetics.

Treatment for Psoriasis

Conventional Medical Treatment

Although psoriasis is currently an incurable disease, there are several ways the symptoms of psoriasis can be relieved for short-term and long-term durations. There are topical medications, systemic medications, as well as light therapy available for the treatment of psoriasis. Treatment of psoriasis not only includes one or more of these treatment options, but also includes diet and lifestyle changes in order to prevent frequent flare-ups and other co-morbidities that may develop in a patient.

For initial therapy of psoriasis, proper diagnosis is of utmost importance. If you suspect that you have psoriasis, it is important that you consult with your doctor. Your doctor will be able to diagnose if you really have psoriasis, or number of other conditions that may present itself like psoriasis (refer to the section, Signs and Symptoms of Psoriasis, for more information). Without proper diagnosis, your treatment plan may not be effective, and may have the potential of worsening your symptoms and condition.

After confirming whether or not you have psoriasis, the doctor will determine the severity of your case; either mild, moderate, or severe. The severity is determined by the percent that your body is covered in psoriatic rashes. For mild cases of psoriasis, less than three percent of the body is affected. In mild cases, the first-line of treatment is topical medications, in the form of creams and ointments. These products can range from soothing lotions to NSAID or retinoid-containing creams to reduce the amount of pain, inflammation, and skin growth. For moderate cases, the coverage of psoriasis is three to ten percent. For severe cases, the body is covered in more than ten percent of psoriatic rashes. In moderate and severe cases, topical medications are not enough to treat psoriasis. Oral and intravenous medications, and light therapies are used to produce more effective and longer-lasting results.

Some medications given to patients with psoriasis include: adalimumab (a TNF-blocker), acitretin (a retinoid), apremilast (treats plaque psoriasis), cyclosporine (an immunosuppressant), etanercept (a TNF-blocker), infliximab (a TNF-blocker), and methotrexate (a DMARD). Retinoids contain vitamin A and work to help improve the condition of the skin and regulates the rate of proliferation of the skin cells. This is beneficial for people with psoriasis because it can reduce the amount of scales and plaque formation. Tumor necrosis factor (TNF) is a significant component of inflammatory response in the body, especially in autoimmune disorders such as psoriasis. By inhibiting TNF, there is suppression of inflammation and hyperactive autoimmune reactions. Disease-modifying antirheumatic drugs (DMARDs) such as methotrexate also work to suppress the autoimmune response, but by inhibiting the enzyme that is required in the formation of folic acid which is necessary for the synthesis of DNA. Immunosuppression is particularly effective in the treatment of psoriatic arthritis. However, like all immunosuppressant drugs, there is an increased risk of opportunistic infections especially with long-term use. Apremilast (brand name: Otezla) is a selective inhibitor of the enzyme PDE4 and a TNF inhibitor, which are both components of inflammatory response. Its main use is to treat psoriasis and psoriatic arthritis. Otezla is costly and only available in select specialty pharmacies in the U.S. and a few other countries.

Light and laser treatments are other forms of treatment for psoriasis, and are typically done in conjunction with a drug regimen. Light or phototherapy, involves the use of controlled exposure to safe amounts of ultraviolet (UV) light. The right amount of UV light can prevent the over-proliferation of the skin cells, causing some potential mutations in the structure of DNA. Treatment is usually painless, but carries with it the same risk of developing skin cancer as would normal exposure to harsh sunlight. Laser light therapy is another supplementary treatment for psoriasis. However, instead of exposing large areas of the body to UV light, it is concentrated to small areas at a time, at different intervals. The benefit of laser therapy is that the plaque or rash is targeted, and limits the exposure of normal, healthy skin from potentially-harmful UV light. Also, because lasers concentrate the light at stronger doses, the light can reach deeper layers of the skin producing more effective and longer-lasting results. Laser light treatment is also relatively painless, however may produce slight warming, redness, and stinging sensation for a while after treatment. Laser therapy sessions last from fifteen to thirty minutes each, and should be repeated every one to three weeks, depending on your doctor’s recommendation.

With research continuing to be done on the mechanisms that govern the development of psoriasis, more medical breakthroughs will be available in the future. There may be an eventual cure to this disease, but at the moment all treatment is aimed at reducing the severity of symptoms, reversing damage to the skin, avoiding triggers, and ultimately improving quality of life.

As in treatment of all medical conditions, it is important to be compliant with your medication and dosing regimen that has been prescribed by your doctor. It is also important that you get regular check-ups from your doctor, and to seek consultation if pain and discomfort persists and/or gets worse overtime. This may be a sign of developing underlying conditions such as psoriatic arthritis, or that the medications you are taking are no longer effective, or that you may have possibly been misdiagnosed. If you get pregnant or plan to become pregnant, it is important that you consult with your doctor because some medications and treatments used in psoriasis may be harmful to a developing fetus. Pregnancy itself may have an effect on your symptoms of psoriasis, either causing remission or flare ups, depending on fluctuation of hormones. It is important that you do not take medications that have been prescribed for someone else, even if you both have psoriasis. Medications, physical treatments, and dosing can vary vastly from person to person and must always be determined by a doctor, not by self-diagnosis.

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Alternative Homeopathic Treatment

Conventional medication and therapies may be costly, especially because psoriasis is a chronic condition that cannot be cured. The medications for the treatment of pain and other symptoms may also cause unwanted side effects and interactions. Some people may opt for more natural alternatives to these drugs and treatment options, or use alternative medicine to supplement their conventional treatment.

The holistic approach is centered on the belief that the body itself is responsible for most of the healing, and that any disharmony within the body will reduce the body’s self-healing capacity. For natural homeopathic medical treatment of psoriasis, it begins like any conventional medical interview with evaluation of the patent’s current disease state. This includes taking the patient’s current and past medical history, medications, allergies, and other pertinent information. However, for the holistic approach to patient care, patients are required to discuss their feelings and experience with their condition on an emotional level. Removal of physical, emotional, and even psychological “toxins” is one of the focal points of homeopathic treatment, and is the preliminary step before any sort of medication or physical remedies should be done.

According to the Alternative Centre of London, their holistic approach begins with something called the “Mora-Therapy Unit” (MTU). The MTU was first developed in Germany by Dr. Franz Morell and engineer Erich Rasche, thus the name “MORA”. The MTU functions as a monitor of the patient’s current medical condition, and to determine any imbalance of the organs within the body. It is used as a preventative medical tool. The MTU is small machine with probes that registers the electro-magnetic fields of each organ. Knowledge of acupuncture pressure points which correspond to each organ is essential in placing the probes; no needles are used in this procedure. The MTU reads results from a scale of 0 to 100, with a normal reading being 50. Any deviation from 50 would indicate excessive or diminished levels of energy coming from the particular organ. After the readings have been completed, the results are interpreted, and the underlying cause of the disease is determined. Unlike conventional medicine practices, where abnormalities in a particular organ system indicate a problem of the organ itself, alternative medicine follows a less direct approach. In the holistic approach, if the energy system of the lungs is out of balance, this could indicate that a patient is a smoker or is exposed to pollutants which are damaging the lungs, and that this imbalance of energy could be the underlying cause of diseases a patient is experiencing, such as psoriasis. Therefore, there does not need to be an imbalance in the skin itself in the case of psoriasis.

After the organs that are causing energy disturbances in the patient have been identified, they can be treated to restore balance and improve the patient’s condition. This requires removal of toxins that may be affecting the unbalanced organs. Removal of toxins usually involves a change in diet, by restricting trigger-inducing food and food that are full of preservatives and artificial additives. Preparation methods of food are also included in changes in a patient’s diet, avoiding the use to microwaves and overcooking vegetables. The environment a person lives in can also contribute to the number of toxins that can build up in their body. These toxins can come in the form of pollution, chemicals, electro-magnetic pollution, and geopathic stress. However, changing locations is much more complicated and expensive than changes in diet. Holistic medicine suggests that maintaining a clean personal space, reduction of use and proper placement of electronic devices, and limited use of chemical cleaners can greatly improve a patient’s condition. Maintaining a positive attitude and having a strong support group is also an important aspect of the healing process in holistic medicine.

Medical treatment in the holistic approach to medicine does not use synthetic drugs or injections, but rather the use of plant-based mixtures either for ingestion or topical application. Some materials used to naturally treat psoriasis include: Dead Sea salts, essential oils from plants, and natural shampoos and soaps. Patients are encouraged to visit health spas, and allow the healing powers of natural hot springs to help relieve their symptoms and get rid of excess toxins.

To be noted though, that many of these natural alternatives are not approved or regulated by the Food and Drug Administration (FDA), and therefore should be taken with caution. If you are taking conventional medications, either for psoriasis or other diseases, it may have adverse reactions with herbal supplements. It is still ideal to consult with a doctor prior to taking any sort of medication or major diet and exercise changes. Some homeopathic practitioners have claimed that their holistic approach to medicine has been able to cure patients of their psoriasis, but there is no sufficient evidence and statistics to validate or refute these claims. Long-term remission of symptoms does not necessarily equate to cure of a disease.

References

  • Ash, Z., & Emery, P. (2013, September). Psoriatic Arthritis. Retrieved from American College of Rheumatology: http://www.rheumatology.org/I-Am-A/Patient-Caregiver/Diseases-Conditions/Psoriatic-Arthritis
  • Dr. James L. Wilson. (n.d.). FAQ on Adrenal Fatigue. Retrieved from Adrenal Fatigue: The Source on Adrenal Fatigue: https://adrenalfatigue.org/faq-on-adrenal-fatique/
  • Finlay, A. (2015, June 24). Why Psoriasis and Asthma Often Co-Exist. Retrieved from New Life Outlook: http://psoriasis.newlifeoutlook.com/why-psoriasis-and-asthma-often-co-exist/
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  • Mayo Clinic Staff. (2015, June 17). Diseases and Conditions : Psoriasis. Retrieved from Mayo Clinic: http://www.mayoclinic.org/diseases-conditions/psoriasis/basics/definition/con-20030838
  • Mescher, A. L. (2013). Junqueira’s Basic Histology Text & Atlas (13th ed.). New York, USA: McGraw-Hill Education.
  • National Psoriasis Foundation/USA. (2016). About Psoriasis. Retrieved from National Psoriasis Foundation: https://www.psoriasis.org/about-psoriasis
  • Silver, N. (2016, January 13). Does Candida Cause Psoriasis? Retrieved from Healthline: http://www.healthline.com/health/psoriasis-and-candida#1