Psoriasis is an inflammatory, immune-mediated disease that causes a skin rash. Psoriasis flares have many triggers, one of which is allergies.

An immune-mediated condition is one in which inflammation occurs due to a dysfunction of the immune system. Both psoriasis and allergies result from immune system dysregulation, although they’re not quite the same.

Psoriasis is a chronic condition in which the immune system overreacts, causing skin cells to multiply too quickly and form a scaly rash. Some experts believe that infection-fighting cells mistakenly attack healthy cells.

Allergies occur when the immune system overreacts to allergens, like pollen or dust mites. The result is symptoms that can include:

  • a runny nose
  • wheezing
  • rash

This article reviews the connection between allergies and psoriasis, along with how to tell the difference and treat each condition.

Seasonal allergies have a range of symptoms:

  • Nasal symptoms: Sneezing, runny nose, and congestion are common allergy symptoms, as well as itchy eyes, nose, and mouth.
  • Asthma symptoms: Wheezing and shortness of breath are examples of asthma symptoms that can be linked to allergies.
  • Cough: An allergy cough might be chronic and dry, or it might occur more frequently in certain environments or during specific seasons.
  • Fatigue: When allergy symptoms interfere with sleep, fatigue may result.
  • Headaches: Migraine attacks and sinus headaches can be linked to allergies.
  • Rash: Hives, bumps, redness, and itching are common features of an allergic rash.

Fever isn’t an allergy symptom. If other allergy symptoms occur with fever, they might have another cause such as infection.

Psoriasis can appear in different forms on various parts of the body:

  • plaques, which are scaly lesions on the skin
  • nail dents or pits
  • pus-filled blisters
  • skin worn into smooth patches in areas where there is friction
  • a red rash over the entire body that can cause fever and dehydration

The whole-body rash known as erythrodermic psoriasis is serious and requires medical attention.

Allergies can sometimes contribute to psoriasis flares.

Itchy allergy hives can prompt a scratch response, which may lead to skin injury. Psoriasis flares can result from skin injuries such as:

  • scratches
  • insect bites
  • vaccinations
  • sunburns

Mast cells

Mast cells are immune cells located wherever antigens from the environment can enter the body, such as in the:

  • respiratory system
  • gastrointestinal tract
  • skin

Mast cells contain granules that store inflammatory substances like histamine, cytokines, and heparin. Histamine release from mast cells can lead to hives in allergic reactions.

Sometimes mast cell activation can result in deeper and prolonged skin swelling that can cause skin issues like eczema or atopic dermatitis.

A 2021 study found that mast cells are also active in psoriasis lesions, in contrast to their resting state in unaffected skin. Not only do mast cells become active in psoriasis lesions, but they also recruit other immune cells that produce inflammation.

Vitamin D

Both psoriasis and allergies may be linked to deficiencies in vitamin D.

A 2016 study found that vitamin D deficiencies may play a role in several conditions, including:

  • lung disease
  • respiratory infections
  • asthma
  • atopic dermatitis
  • food allergies

The study authors theorize that vitamin D might regulate epigenetic changes that lead to allergic conditions.

Severe psoriasis may lead to a vitamin D deficiency, according to a 2017 study.

Study authors theorize that the vitamin D deficiency stems from a loss of nutrients resulting from the accelerated rate of skin shedding seen in psoriasis.

Experts believe that the relationship between low vitamin D and psoriasis might work in both directions, and that a preexisting deficiency in vitamin D might also be one of the factors that lead to psoriasis.

Vitamin D supplementation may benefit people living with psoriasis by preventing conditions like high blood pressure and metabolic syndrome.

There are differences between a psoriasis rash and hives from allergies that can make the two conditions identifiable.

scaly, dry, or cracked skinflat and smooth rash
appears graduallyappear quickly
lasts for several weeks or moreintermittent and may disappear within hours
sometimes bleedsonly bleeds when scratched excessively

Hives are more common than psoriasis, which affects only around 3% of adults in the U.S. Hives, on the other hand, affect an estimated 20% of people.

Psoriasis and allergy hives have similar characteristics as well. They can both cause itching and can be widespread or confined to one area of the body.

Doctors use a physical exam, health history, and sometimes a skin sample analysis to make a diagnosis.

Treating allergies can sometimes soothe psoriasis symptoms.

The use of antihistamines is a common allergy treatment. A 2017 study found that antihistamines also reduced the itching experienced by participants with psoriasis.

The study found evidence to suggest that psoriasis mast cells could be functionally hyperreactive, and histamine might play a role in the development of psoriasis.

Treating allergy itchiness can also prevent psoriasis from worsening.

The American Academy of Dermatology Association recommends against scratching allergy hives because this can trigger a psoriasis flare. Instead, people living with allergy itch can use skin-calming techniques such as:

  • applying an ice pack or cool, wet cloth to the itchy area
  • moisturizing skin
  • taking an oatmeal bath
  • applying cooling agents like calamine or menthol
  • using a topical anesthetic containing pramoxine

Psoriasis treatment includes topical, oral, or injectable medications such as:

  • corticosteroids
  • medications containing vitamin D
  • retinoids
  • tar products
  • immunosuppressants
  • biologics

Doctors sometimes use phototherapy to treat psoriasis when the rash covers a large area.

Psoriasis and allergies both stem from immune system irregularities.

For some people, allergies can trigger psoriasis flares. Skin injury from scratching allergy hives is one reason for this connection.

Treating allergies may reduce psoriasis symptoms. Antihistamine can reduce itching in both allergies and psoriasis.