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Is your itchy skin an allergic reaction — or the sign of an underlying skin condition? For someone with new or emerging symptoms, making the distinction can be challenging. Allergic reactions can cause itching, discoloration, and irritation — but then again, so can psoriasis.
While psoriasis and allergic reactions may appear similar, they have very different causes, symptoms, and treatments. Your doctor will be able to diagnose which condition you have based on different factors. As always, if you’re experiencing new or worsening skin symptoms, check in with your doctor or dermatologist for medical advice.
Psoriasis is a chronic skin condition that affects between 2 percent and 3 percent of the global population. It’s an autoimmune disease, meaning it occurs when the immune system attacks the body’s own healthy cells (in this case, the skin cells). The overactive immune response leads to inflammation and the accelerated production of skin cells.
In people with psoriasis, the skin builds up more quickly than it can shed, resulting in characteristic patches of thick, scaly skin known as plaques. Discoloration associated with psoriasis can vary, depending on skin color. It can present as red or pink in people with lighter skin and as purple or dark brown in those with darker skin.
Skin allergies occur when a person’s immune system has an unusual reaction to something in the environment. These environmental triggers can vary widely. A person might be allergic to certain types of plants, foods, medications, or animals.
The symptoms of allergic reactions can also differ from person to person. However, common allergic skin reactions include:
Both psoriasis and skin allergies can cause discoloration, itching, swelling, and discomfort. However, they tend to do so in very different ways.
For example, most people with psoriasis experience these symptoms when dry, scaly, thick patches of skin called plaques form on their skin. These plaques tend to be itchy, are often covered with silvery-white scales, and often appear on areas such as the elbows, knees, legs, face, palms, and feet.
This isn’t to say that all people with psoriasis will experience the same set of symptoms. While plaque psoriasis affects roughly 90 percent of people with psoriasis, there are other types of psoriasis, each with its own distinct symptoms. Guttate psoriasis, for example, causes small, discolored, scaly lesions to appear on the trunk (torso), arms, and legs, while erythrodermic psoriasis can cause a discolored burning rash all over the body.
Psoriasis symptoms vary in their severity and location on the body. People with psoriasis also experience periodic flare-ups, during which symptoms appear or worsen, and periods of remission, when symptoms fade.
Skin-allergy symptoms, on the other hand, usually only appear when a person is exposed to a substance their body can’t tolerate. The extent and severity of the skin irritation associated with an allergic reaction will depend on how sensitive you are to a given allergen.
Allergic reactions whose symptoms may be confused with psoriasis include hives, eczema, and contact dermatitis.
Hives, also known as urticaria, are discolored, raised, and itchy lumps that blanch (turn white) when pressed. These lumps can appear anywhere on the body and often range in size. Typically, hives that appear as an allergic reaction will disappear within a few hours or days. The raised bump one may experience from a bug bite is a hive and is an immediate allergic reaction of the skin.
Dermatitis occurs when the skin becomes inflamed and produces an itchy, discolored, and scaly rash. Atopic dermatitis is commonly referred to as eczema. The most common symptom of mild eczema is dry, itchy skin. However, more severe cases of eczema can lead to symptoms that overlap with those of psoriasis, such as cracked skin and discolored, itchy patches of skin. A key differentiator from psoriasis is that an eczema rash may ooze clear or yellowish fluid. Atopic dermatitis is much more commonly itchy when compared to psoriasis.
As its name suggests, contact dermatitis is a skin rash that occurs when a person comes into contact with a substance they are allergic to. Their immune system reacts, causing itchy discolored blisters. Poison ivy the classic example of a substance that causes allergic contact dermatitis.
Doctors aren’t sure exactly what causes psoriasis. However, they do know it is an immune-mediated condition, or one that occurs as the result of an overactive immune system response. In people with psoriasis, T cells (white blood cells that attack viruses) begin attacking healthy skin cells. These attacks lead the body to produce more skin cells at a faster rate than normal. The skin does not shed quickly enough to keep up, resulting in an accumulation of immature cells on the skin’s surface. These accumulations create the toughened, scaly discolored patches known as plaques.
Because psoriasis runs in families, researchers believe that it may be genetic (inherited). However, more research is needed to confirm genetics as a cause. Other factors that can worsen or trigger psoriasis flare-ups include:
Like psoriasis, skin allergies may be triggered by environmental or lifestyle factors. Many potential allergens exist, which is why it is so important to work with an allergist or dermatologist when you’re unsure of what is causing the allergic reaction in your skin.
That said, some allergic responses are more likely to be caused by certain triggers, which mostly differ from psoriasis triggers.
Eczema, for example, is often triggered by:
Eczema typically begins in childhood and is much more common among children than adults, as many people outgrow the condition.
Contact dermatitis may be triggered by material allergens such as:
Finally, hives may result from:
Whereas hives occur within minutes of exposure, allergic contact dermatitis usually occurs 24 to 48 hours after exposure.
Generally, people with psoriasis tend to have thicker plaques and dry scaling compared to people with eczema. Rashes in eczema may also ooze fluid. If a doctor can’t make a diagnosis by looking at the rash, they may take biopsies (skin samples) to confirm which condition is causing plaques. A punch biopsy is usually performed.
As one MyPsoriasisTeam member shared, the diagnostic process can be challenging but worth it, once you find the right care: “I was misdiagnosed with eczema for years. I am so happy to be referred to a specialist to find treatment. I feel so blessed to finally see an answer. I look forward to treatment and learning more.”
Because psoriasis is an autoimmune disorder, it may require treatment with medications that target the immune system (known as immunomodulators). Unlike psoriasis, skin allergies may be prevented entirely by avoiding triggers.
Treatment options for psoriasis vary depending on the severity of a person’s condition, where symptoms appear, and other factors relating to their overall health and circumstances.
Generally, doctors begin treatment by prescribing topical treatments, such as steroid creams, moisturizers, and medicated lotions. If topical treatments don’t provide enough relief, doctors may also recommend UV light treatments (phototherapy), which use targeted artificial light to treat affected areas. Some people may even find some relief from spending time outdoors. “The sun has always helped the most with my psoriasis,” shared one MyPsoriasisTeam member.
People with moderate to severe cases of psoriasis may need to consider stronger treatments. Cyclosporine-based medications, for example, may alleviate severe psoriasis. The immunomodulator injection Otrexup (methotrexate) may be used to treat flare-ups and prevent plaque buildup by suppressing the immune system.
More recently, a class of medications called biologics are being used to control psoriasis. Often administered as injections, biologics work by modulating the overactive part of the immune system.
Read more about treatment for psoriasis.
An allergist or dermatologist can help you determine which allergens you’re reacting to and help you manage your symptoms. Patch testing — which entails affixing patches containing samples of potential allergens to a person’s back — is a common approach.
The easiest treatment for skin allergies is avoiding your triggers. That said, there are a few steps you can take to alleviate your symptoms if you’re unsure of what you’re allergic to or can’t avoid triggers.
Living with psoriasis is easier when you have the support of others who understand what it means to manage a chronic skin condition. MyPsoriasisTeam is the social-media platform made exclusively to support and connect people living with psoriasis. You can take part in conversations, offer advice, and build real friendships with people who truly understand what you’re going through.
Have you ever mistaken an allergic reaction for psoriasis (or vice versa)? Let us know in the comments below, or start a new conversation thread on MyPsoriasisTeam.