Allergic skin rashes can result from a variety of causes producing a range of symptoms from an itchy irritating rash to life threatening swelling. All of the symptoms originate from a trigger to your immune system that releases histamine and other chemicals in the body. Most of these allergic skin reactions will resolve without long-term effects when the primary allergen is removed from your environment.
Types
According to Merck Manuals Online Medical Library, there are several types of allergic skin reactions. A drug allergy reaction happens when your immune system reacts to a medication, either prescription or over-the-counter. Contact dermatitis causes itching, red, raised rashes that often include blisters when your skin comes in direct contact with an allergen. The most common contact allergens include poison ivy, fragrances, preservatives, nickel, rubber and dyes. Atopic dermatitis is a chronic inflammation of the upper layers of the skin that affects between 9 percent and 30 percent of children. Food allergies and anaphylactic responses are two other common types.
Effects
The skin effect for these allergic rash reactions will be slightly different based on the origin of the allergen. According to American Academy of Dermatology, a contact dermatitis will cause swollen tiny blisters that break and leave crusts on the skin directly over the area that came in contact with the allergen. This is significantly different from the effect of a reaction to drugs, food or atopic dermatitis. According to U.S. National Library of Medicine, these reactions happen when your immune system reacts to an internal allergen and the result is typically a minor rash or skin hives over the trunk and extremities.
Features
Allergic skin rashes are commonly minor reactions that are self-limiting. According to the American Academy of Dermatology, contact dermatitis will resolve over two weeks after the offending allergen has been removed. However, if you are exposed to an allergen over a long period of time, the skin can become thicker, red and scaly. Later the skin can darken and become leathery. Atopic dermatitis has a significantly different presentation, according to Merck Manuals Online Medical Library. Color, intensity and location of the rash will vary between people but the rash will always be itchy. Uncontrolled scratching will make the problem worse, leaving the skin open to bacterial infections or widespread infection with herpes simplex virus. Your condition may worsen with emotional stress, changes in temperature, bacterial infections or contact with clothing that irritates the skin.
Time Frame
According to the U.S. National Library of Medicine, an allergic drug rash may not appear after the first exposure to a medication. It may take several doses or even a week before your immune system is triggered and you break out into a rash. Contact dermatitis often appears more quickly, according to the American Academy of Dermatology. A reaction to poison ivy can become visible within 24 hours of exposure. According to Merck Manuals Online Medical Library, a rash from a food allergy can be immediate, such as with an anaphylactic reaction to protein in eggs, peanuts or seafood. The reaction can also occur over a 24-hour period.
Treatments
According to Merck Manuals Online Medical Library, the treatment for most allergic rash responses is to remove the offending allergen and give supportive care to the area affected. You may find relief from the itching and burning with a colloidal oatmeal bath or cool compresses over the area. Your doctor may recommend the use of antihistamine medication to relieve the itching and swelling as well.
