3 Common Allergy Rashes—and What They Look Like

The list of things your body can have an allergic reaction to is long: cats and dogs, jewelry, soap, plants—they can all spark an overreaction of your immune system, sometimes in the form of a rash.

An allergic reaction occurs when your body's immune system reacts to a harmless substance—such as certain foods, pollen, or pet dander. Allergic reactions don't just affect the skin—they can also impact the nose, throat, lungs, ears, sinuses, and stomach lining.

Allergy rashes can be uncomfortable and can lead to infections, scarring, or other health complications— and shouldn't be ignored. Below, you'll find info on three common allergy rashes—eczema, contact dermatitis, and hives—including treatment options and advice on what to do if the rash doesn't go away after treating it.

Atopic Dermatitis

Atopic dermatitis is a type of eczema which is far more common among children than adults. It affects up to 20% of children but only affects 1% to 3% of adults and that half of patients who have eczema also experience food allergies and hay fever.

The following are symptoms of eczema according to the National Eczema Association (NEA):

• Itchy skin
• Sensitive skin
• Dry skin
• Inflamed skin
• Discolored skin
• Rough, scaly, or leathery patches of skin
• Crusting
• Oozing
• Areas of swollen skin

The NEA says that some people with eczema will experience all of the above symptoms while others will experience just one or two.

"Eczema [presents as a] persistent, all-over rash," Ronald Purcell, MD, an allergist at Cleveland Clinic, told Health. It used to be thought that food allergies cause eczema, but in fact, that's not true. People with eczema frequently have food allergies and other allergic conditions, but food allergies don't cause eczema.

But food isn't the only trigger: "Seasonal allergies could certainly cause eczema exacerbation," Kanwaljit Brar, MD, an allergist with advanced training in dermatology at NYU Langone, told Health.

Where the eczema breakout occurs might depend on the age of the patient, per the AAAAI, which states that the rash usually forms on the knees, elbows, cheeks, and scalp in children but might also occur on the face, wrists, and neck of adults, in addition to their elbows and knees.

The AAAAI says that avoiding triggers is key to preventing eczema flares. A number of treatments are available for treating eczema, and common options include topical moisturizers that lessen itching and hydrate the skin. Topical steroids, which are anti-inflammatory medications, can help take away the rash caused by eczema. And good skin hydration is important because dry skin can also cause itching which can lead to a rash, creating a vicious itch-scratch cycle.

Allergic Contact Dermatitis

Allergic contact dermatitis is an allergy-related rash that's caused by coming into contact with an allergen. A number of triggers can cause allergic contact dermatitis, including shampoos, makeup products, and nickel jewelry, Dr. Purcell said. Poison ivy and certain fragrances are some of the leading causes of allergic contact dermatitis.

You may not see a reaction immediately after coming into contact with the product that contains the allergen. In fact, it could take several days after the exposure for the rash to develop.

Dr. Brar added that contact dermatitis is often caused by something you wouldn't consider when thinking about a potential list of allergens, such as "your bed linens, a new piece of furniture in the home, a new pair of shoes, the cleaner you're using for your dishes."

There's also a rare form of contact dermatitis that doesn't require direct contact with the skin to cause a flare, Dr. Brar said. It's called airborne contact dermatitis and occurs from coming into contact with aerosolized plant resins from sunflowers, ragweed, and goldenrod. Although rare, airborne contact dermatitis can cause a rash on the face, neck, and eyelids, Dr. Brar said.

Contact dermatitis is common and individuals with chronic skin problems like sensitive skin might be more prone to the condition. Symptoms of contact dermatitis include:

• Red rash
• Blistering, oozing, or swollen rash
• Stinging or burning rash
• Hive-like rash
• Painful rash
• Itchy rash

Avoiding triggers—if you can identify them—is key in managing allergic contact dermatitis. Other treatments include cool packs, lotions, colloidal oatmeal baths, topical steroids, or oral steroids.

Hives

Environmental allergens like cats and dogs can cause hives, which present as slightly raised, itchy red bumps, Dr. Purcell said. "They're temporary; they go away after exposure is eliminated," Dr. Purcell added.

Acute allergic hives can be caused by a reaction to certain foods and medicines. Potential triggers include:

• Pollen
• Insect bites
• Medicines
• Animal dander
• Nuts, eggs, milk, fish, shellfish, and other foods

When hives are a chronic condition, there can be causes other than allergens, including emotional stress and excessive perspiration.

According to the ACAAI, the symptoms of hives are as follows:

• Raised itchy bumps that are skin-colored or red
• Blanching (meaning that, when pressure is applied, the center of the hive will turn white)

Treatment options for hives include antihistamines, steroids, an injectable medication called omalizumab that treats chronic hives, and other anti-inflammatory medications. If these treatment options don't work, an antibiotic called dapsone may be used to treat chronic hives.

If you know cats cause you to break out in hives, and you plan on visiting a friend who has a cat, it might be worth considering taking an antihistamine before you arrive at the friend's home, Dr. Purcell suggested. Avoiding triggers that cause hives is also key in managing the condition, Dr. Purcell added.

When To Get Medical Help

Luckily, rashes caused by allergies can often be treated from the comfort of your own home, and some might clear up as soon as the allergen is removed from your environment. Dr. Purcell said it's important to see a healthcare provider if your rash doesn't respond to treatments that usually work, like topical steroids or taking an antihistamine.

And if you can't figure out what's causing your rash, you should consult a healthcare provider to determine what's triggering your symptoms.

If you can, try making an appointment with a skincare specialist, like a dermatologist, rather than visiting an urgent care for help with a rash caused by an allergen, Dr. Brar recommended. That said, if you are experiencing serious symptoms, like shortness of breath, you should seek help as quickly as possible rather than waiting for an appointment with a specialized doctor.