Skin rashes can occur from a variety of factors, including infections, heat, allergens, immune system disorders and medications. One of the most common skin disorders that causes a rash is atopic dermatitis (ay-TOP-ik dur-muh-TI-tis), also known as eczema.

Atopic dermatitis is an ongoing (chronic) condition that makes skin red and itchy. Most often it appears as patches on the hands, feet, ankles, neck, upper body and limbs. It tends to flare up periodically and then subside for a time.

At-home interventions, such as avoiding harsher soaps and detergents or other irritants and applying creams or lotions, can lessen symptoms and reduce the risk of flare-ups. Medicated anti-itch creams or ointments also can lessen symptoms.

Christmas tree rash (pityriasis rosea)

Christmas tree rash (pityriasis rosea) is a fine, itchy, scaly rash that usually appears first as a single patch on the chest, abdomen or back. After this first appearance (herald patch), the rash may spread as small patches to other parts of the back, chest and neck. The rash may form a pattern on the back that resembles the outline of a Christmas tree.

Pityriasis rosea usually goes away without treatment in four to 10 weeks, but it can last months. Medicated lotions may lessen itchiness and speed the disappearance of the rash. Often, though, no treatment is required.

Contact dermatitis

Contact dermatitis is a rash caused by direct contact with or an allergic reaction to certain substances. Irritant contact dermatitis (A) usually produces a dry, scaly, non-itchy rash. Many substances, such as cleaning products or industrial chemicals, that you come into contact with cause this condition. The irritant will cause a rash on anyone exposed to it, but some people’s skin may be more easily affected.

Allergic contact dermatitis (B) produces a very itchy, red rash with bumps and sometimes blisters. Common allergy-causing agents (allergens) are latex rubber, nickel and poison ivy. Allergic contact dermatitis develops after your initial exposure to the allergen.

To treat your rash, try to figure out what caused it and avoid that substance. You can also apply medicated cream to help improve symptoms.

Drug rash

A rash may occur as a side effect of taking a drug or as an allergic reaction to it. A drug rash may be caused by many different medications, including antibiotics and water pills (diuretics). Some drugs are more likely to produce a rash if the skin is exposed to sunlight.

A drug rash, which usually starts within the first week of taking a new medication, often begins as red spots. The spots spread and merge, covering large areas of the body. If you stop taking the drug that caused the rash, it will usually clear up in days to weeks.

Rarely, a drug rash is part of a more serious, potentially life-threatening allergic reaction that affects the respiratory system and other organs. These severe reactions require emergency care.

Heat rash (miliaria)

Heat rash (miliaria) occurs when the flow of sweat is obstructed, usually due to hot, humid weather or overdressing.

Prickly heat (miliaria rubra) (A) is a type of heat rash that appears as clusters of small, red bumps that produce a pricking or stinging sensation. Miliaria crystalline (B) appears as clear, fluid-filled bumps that generally produce no other signs or symptoms.

Heat rash isn’t serious and usually resolves when the affected area cools. Cool compresses or a cool bath might help. You can prevent heat rash by wearing loose, lightweight clothing and avoiding excessive heat and humidity.

Intertrigo

Intertrigo (in-tur-TRY-go) is inflammation caused by skin-to-skin friction, most often in warm, moist areas of the body, such as the groin, between folds of skin on the abdomen, under the breasts, under the arms or between toes. The affected skin may be sensitive or painful, and severe cases can result in oozing sores, cracked skin or bleeding.

Intertrigo usually clears up if you find a way to keep the affected areas as clean and dry as possible. Try wearing loosefitting clothing and using powder to reduce skin-to-skin friction in affected areas. Weight loss may be helpful as well.

Sometimes, a bacterial or fungal infection can develop at the site of your intertrigo. If this happens, you may need a medication to heal your skin.

Lichen planus

Lichen planus (LIE-kun PLAY-nus) is an inflammatory condition that can affect your skin and mucous membranes. On the skin it usually appears as purplish, often itchy, flat-topped bumps (lesions). In your mouth, vagina and other areas covered by a mucous membrane, lichen planus forms lacy white patches.

The condition may develop gradually over a couple of months. After that, it rarely worsens, but it may persist for months or years. You can usually control mild lichen planus symptoms on the skin, such as stinging and itching, by applying cool compresses or aloe vera gel. More-severe symptoms may require drug treatment. Lesions on mucous membranes tend to take longer to heal and often recur.

Psoriasis

Psoriasis (suh-RIE-uh-sis) is the rapid buildup of rough, scaly skin that occurs when the life cycle of skin cells rapidly increases. The accumulation of dead skin cells results in thick, silvery scales and itchy, dry, inflamed patches that are sometimes painful.

The condition tends to flare up periodically and then subside for a time.

For some people, psoriasis is a mild nuisance. For others, it can be disabling, affecting extensive areas of skin for long periods and often occurring with a distinct type of arthritis (psoriatic arthritis). Topical medications and light therapy may help reduce signs and symptoms of the skin lesions.

Everything you need to know about allergies

Allergies are hypersensitive responses from the immune system to substances that either enter or come into contact with the body.

These substances commonly include materials such as pet dander, pollen, or bee venom. Anything can be an allergen if the immune system has an adverse reaction.

A substance that causes an allergic reaction is called an allergen. Allergens can be found in food, drinks, or the environment.

Many allergens are harmless and do not affect most people.

If a person is allergic to a substance, such as pollen, their immune system reacts to the substance as if it was foreign and harmful, and tries to destroy it.

Research indicates that 30 percent of adults and 40 percent of children in the United States have allergies.

Fast facts on allergies

• Allergies are the result of an inappropriate immune response to a normally harmless substance.
• Some of the most common allergens are dust, pollen, and nuts. They can cause sneezing, peeling skin, and vomiting.
• Anaphylaxisis a serious allergic reaction that can be life-threatening.
• To diagnose an allergy, a clinician may take a blood sample.
• The symptoms of an allergy can be treated with drugs. However, the allergy itself requires desensitization.
• Anaphylaxis requires emergency treatment. Epinephrine injectors can help reduce the severity of an anaphylactic reaction.

What is an allergy?

Allergies are a very common overreaction of the immune system to usually harmless substances.

When a person with an allergy comes into contact with an allergen, the allergic reaction is not immediate. The immune system gradually builds up sensitivity to the substance before overreacting.

The immune system needs time to recognize and remember the allergen. As it becomes sensitive to the substance, the immune system starts making antibodies to attack it. This process is called sensitization.

Sensitization can take a few days or several years. In many cases, the sensitization process is not completed. The patient experiences some symptoms but not a full allergy.

Allergies may also be seasonal. For example, hay fever symptoms can peak between April and May, as the pollen count in the air is much higher.

Symptoms

An allergic reaction causes inflammation and irritation. The signs and symptoms depend on the type of allergen. Allergic reactions may occur in the gut, skin, sinuses, airways, eyes, and nasal passages.

Allergic reactions may be confused for other conditions. Hay fever, for example, creates similar irritations to the common cold but the causes are different.

Below is a range of various triggers and the symptoms they regularly cause in people who are allergic.

Dust and pollen

• blocked nose
• itchy eyes and nose
• runny nose
• swollen and watery eyes
• cough

Skin reactions

• flaking
• itching
• peeling
• rashes

Food

• vomiting
• swollen tongue
• tingling in the mouth
• swelling of the lips, face, and throat
• stomach cramps
• shortness of breath
• rectal bleeding, mainly in children
• itchiness in the mouth
• diarrhea

Insect stings

• wheezing
• swelling at the site of the sting
• a sudden drop in blood pressure
• itchy skin
• shortness of breath
• restlessness
• hives, a red and very itchy rash that spreads across the body
• dizziness
• cough
• chest tightness
• anxiety
• possible anaphylaxis

Medication:

• wheezing
• swollen tongue, lips, and face
• skin rash
• itchiness
• possible anaphylaxis

Anaphylaxis

Anaphylaxis is a quickly escalating, serious allergic reaction that sets in rapidly. It can be life-threatening and must be treated as a medical emergency.

This type of allergic reaction presents several different symptoms that can appear minutes or hours after exposure to the allergen. If the exposure is intravenous, onset is usually between 5 to 30 minutes. A food allergen will take longer to trigger anaphylactic reaction.

Causes

A particular antibody called immunoglobin (IgE) causes allergic reactions. Antibodies are released to combat foreign and potentially harmful substances in the body.

IgE is released to destroy the allergen and causes the production of chemicals that trigger the allergic reaction.

One of these chemicals is called histamine. Histamine causes tightening of the muscles in the airways and the walls of blood vessels. It also instructs the lining of the nose to produce more mucus.

Risk factors

The following can be risk factors for developing allergies:

• a family history of asthmaor allergies
• being a child
• having asthma
• not being exposedto enough sunlight
• having a different allergy
• birth by Caesarean section

The most common allergens

Potential allergens can appear almost anywhere.

Any food can theoretically cause an allergy. Specific components of food can also trigger allergic reactions, such as gluten, the protein found in wheat. The eight foods most likely to cause allergies are:

• eggs, especially egg-white
• fish
• milk
• nuts from trees
• peanuts
• wheat
• soy
• shellfish

Other allergens include:

• animal materials, such as dust mite excrement, wool, fur, dander, or skin flakes, as well as Fel d 1, a protein found in cat saliva
• medications, such as penicillin, salicylates, and sulfonamides
• foods such as corn, celery, pumpkin, sesame, and beans
• insect stings, including wasp and bee sting venom, mosquito stings, and fire ants.
• insect bites from horseflies, blackflies, fleas, and kissing bugs
• cockroaches, caddis and lake flies, midges, and moths
• plant pollens from grass, trees, and weeds
• household chemicals
• metals, such as nickel, cobalt, chromium, and zinc
• latex

Diagnosis

The doctor will ask the patient questions regarding symptoms, when they occur, how often, and what seems to cause them. They will also ask the person with symptoms whether there is a family history of allergies, and if other household members have allergies.

The doctor will either recommend some tests to find out which allergen is causing symptoms or refer the patient to a specialist.

Below are some examples of allergy tests:

• Blood test: This measures the level of IgE antibodies released by the immune system. This test is sometimes called the radioallergosorbent test (RAST)
• Skin prick test: This is also known as puncture testing or prick testing. The skin is pricked with a small amount of a possible allergen. If the skin reacts and becomes itchy, red, and swollen, it may mean an allergy is present.
• Patch test: A patch test can identify eczema. Special metal discs with very small amounts of a suspected allergen are taped onto the individual’s back. The doctor checks for a skin reaction 48 hours later, and then again after a couple of days.

The American College of Allergy, Asthma and Immunology can help you find a certified allergist.

Even if the patient knows what triggers the allergy, the doctor will carry out tests to determine which particular substance is causing symptoms.

Treatment

The most effective treatment and management of an allergy is avoidance of the allergen.

However, sometimes it is not possible to completely avoid an allergen. Pollen, for example, is constantly floating in the air, especially during hay fever season.

Medications

Drugs can help treat the symptoms of an allergic reaction, but they will not cure the allergy. The majority of allergy medications are over-the-counter (OTC). Before taking a particular type of medication, speak to a pharmacist or doctor.

• Antihistamines: These block the action of histamine. Caution is recommended, as some antihistamines are not suitable for children.
• Decongestants: These can help with a blocked nose in cases of hay fever, pet allergy, or dust allergy. Decongestants are short-term medications.
• Leukotriene receptor antagonists, or anti-leukotrienes: When other asthma treatments have not worked, anti-leukotrienes can block the effects of leukotrienes. These are the chemicals that cause swelling. The body releases leukotrienes during an allergic reaction.
• Steroid sprays: Applied to the inside lining of the nose, corticosteroid sprays help reduce nasal congestion.

Immunotherapy

Immunotherapy is also known as hyposensitization. This type of therapy rehabilitates the immune system. The doctor administers gradually increasing doses of allergens over a period of years.

The aim is to induce long-term tolerance by reducing the tendency of the allergen to trigger IgE production.

Immunotherapy is only used to treat severe allergies.

How to prevent allergies

There is no way to prevent an allergy. However, it is possible to limit symptoms.

Even though treatments can help alleviate allergy symptoms, patients will need to try to avoid exposure to specific allergens. In some cases, this is not easy. Avoiding pollen in late spring and summer is virtually impossible, and even the cleanest houses have fungal spores or dust mites.

If you have friends or family with pets, avoiding them might be difficult. Food allergies can be challenging to manage because traces of allergens can appear in unlikely meals. However, being vigilant about checking food packages can be a key way to avoid consuming certain allergens.

Make sure you receive proper allergy testing and know what substances to avoid.