An allergy is an overreaction of the body to any substance that it sees as foreign. The offending substance may be eaten, touched, breathed or injected. The body may react by developing a hay fever-type reaction with runny nose, scratchy throat and watery eyes or a more serious reaction including difficulty breathing or swallowing. However, many allergies manifest as skin rashes. According to the Asthma and Allergy Foundation of America, approximately 7 percent of allergy sufferers complain of skin allergies as their main allergy.
Common Allergens
Allergens are the substances to which people are allergic. The most common allergens to trigger skin reactions include poison ivy, oak and sumac, notes the Asthma and Allergy Foundation of America.
Other common culprits are cockroaches and dust mites, latex, dyes, preservatives, fragrances, and certain foods. Certain metals, such as nickel, are common triggers of an allergic rash, according to the American Academy of Dermatology or AAD.
Rash appearance
An allergic skin rash typically becomes red, swollen, and itchy. Blisters and red bumps may develop. If left untreated, a chronic rash can cause thickened, scaly or crusted skin, notes the AAD.
The rash may be all over the body, as in the case of a medication or food allergy, or simply localized to the area in contact with the offending agent, such as an allergy to metal. Occasionally, people may inadvertently spread the rash themselves when they itch the rash caused by a substance such as poison ivy.
Diagnosis
Sometimes the cause of a rash is fairly obvious. For example, a red blistering rash may occur directly underneath a new piece of nickel-containing jewelry, or hives may develop after taking a new medication. Occasionally, however, testing is needed to determine the offending agent. In these cases, a doctor may need to do patch testing or blood work to investigate the source of the rash.
Treatment
Identification and avoidance of the allergic trigger is the most important step in reducing allergic rashes. Once a rash develops, however, cool compresses may be soothing. A topical cream, such as over-the-counter hydrocortisone may help with the itching and redness. Oral antihistamines are also often used to help alleviate symptoms, according to the AAD. Occasionally, a medical provider will prescribe other medications, such as oral or topical cortiscosteroids to treat a severe rash, reports Merck Manual.
More severe reactions
Occasionally, a more severe allergic reaction may occur. This is termed anaphylaxis and often includes hives, swelling, or difficulty breathing or swallowing, This requires immediate medical attention. Epinephrine, typically in the form of an "epi-pen" should be used.
