Psoriasis and atopic dermatitis are common, long-term skin diseases.
Psoriasis and atopic dermatitis are common, long-term skin diseases.

Psoriasis and atopic dermatitis are common, long-term skin diseases. Both are noncontagious. Because both the rashes look somewhat similar, the diagnosis may be difficult at the first glance, and a biopsy of the skin remains the last resort. However, certain things that can help differentiate between the two before the doctor orders a biopsy.

What is more common: atopic dermatitis or psoriasis?

Atopic dermatitis is not only the most common type of eczema but also a skin condition more common than psoriasis in the United States. Psoriasis affects more than 8 million people, whereas atopic dermatitis affects around 16.5 million people.

What does atopic dermatitis look like?

Atopic dermatitis can cause itchy skin with small, red bumps, or red to brownish-gray patches/rash. Itching is often more common and severe than in psoriasis. Scratching can cause the bumps to ooze fluid and crust over.

The condition often begins during childhood and can continue up to adulthood.

Common sites of rash are the cheeks, inside of the elbows, behind the knees, and over the neck.

A person with atopic dermatitis is also more likely to have asthma or hay fever. Moreover, a family history of hay fever or asthma puts the person at higher risk of atopic dermatitis.

What does psoriasis look like?

Red or silvery scales (most commonly round) on the skin are typical features that distinguish psoriasis from atopic dermatitis. The most common type, plaque psoriasis, begins as small red round bumps that grow larger and form a scale. Scratching (often due to itching) can pull the scales off the skin and result in bleeding.

Psoriatic rash or patches can erupt anywhere on the skin, sometimes all over the body (including the nails). However, the common areas are as follows:

  • Scalp
  • Outer elbows
  • Knees
  • Over knuckles
  • Back

The typical age of people who have psoriasis is between 15 and 25 years, but there is no age limit. Recent studies have reported that the condition is becoming more common in people older than 30 years.

In contrast to atopic dermatitis, psoriasis also affects the joints. The condition is known as psoriatic arthritis. Apart from the joints, psoriasis also puts the affected people at a risk of other health conditions that include diabetes, high blood pressure, heart diseases, and Crohn's disease.

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What causes and triggers atopic dermatitis?

Doctors do not know the exact cause of atopic dermatitis. Both genetic and environmental factors are found to be the triggering factors. 

Researchers have come across some genetic mutations that alter the protective layer of the skin. This can allow the skin to be affected by triggers:

  • Environmental factors
  • Irritants (certain fabrics, soaps, chemicals, and household cleaners)
  • Food allergens (milk, eggs, and peanuts)

The allergens differ among people. Other factors that trigger atopic dermatitis include stress, infections, and exposure to heat.

People with dry skin or those living in cold, dry regions seem to be more vulnerable to atopic dermatitis.

How are atopic dermatitis and psoriasis diagnosed?

Most of the time, atopic dermatitis and psoriasis are diagnosed from the patient’s history, look, and distribution of the rash.

For atopic dermatitis, doctors may order an allergen test to identify the allergens the patients are sensitive to.

For patients who do not respond to the respective treatments, doctors scrape or cut a small piece of the patchy skin (biopsy). They then send it to the laboratory to look for specific cells under a microscope.

How do atopic dermatitis and psoriasis differ in their treatments?

Many times, doctors treat atopic dermatitis in the same way as they treat psoriasis. The treatments common to both include:

  • Avoidance of triggers and stressors
  • Heavy moisturizers (liquid paraffin, urea, squalene, and beeswax)
  • Corticosteroid cream (especially for atopic dermatitis)
  • Antihistamines (medications to relieve the itching)
  • Topical or oral antibiotics if there is bleeding and associated infection
  • Immunomodulators creams or lotion (drugs that target the immune system) for severe cases; sometimes, pills and injectables are often given for treating severe psoriasis.

Most people with psoriasis feel better when exposed to sunlight and warm climates. This aspect has led to the use of ultraviolet (UV) light therapy, which improves the skin condition in psoriasis.

Atopic dermatitis can flare up when exposed to hot climates (sweating triggers the rash). Light therapy can aggravate or induce the atopic dermatitis rash.

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Medically Reviewed on 2/11/2021
References
National Eczema Association: "Eczema," "Symptoms of Eczema," "Causes & Triggers," "Treatment." https://nationaleczema.org/eczema/

National Psoriasis Foundation: "About Psoriasis," "Life with Psoriasis," "Causes and Known Triggers," "Psoriasis Treatments." https://www.psoriasis.org/about-psoriasis/

Griffiths CE, van de Kerkhof P, Czarnecka-Operacz M. Psoriasis and Atopic Dermatitis. Dermatol Ther (Heidelb). 2017;7(Suppl 1):31-41.

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