Allergic reactions result when the body responds to a typically innocuous foreign substance, called an allergen, as if it was a potential threat. An allergic response involves the release of histamines, chemicals that flood from cells that are reacting to the allergen. Histamines increase the permeability of blood vessels, which allows the increased flow of fluids out of the capillaries and into the affected area. This reaction is responsible for the symptoms associated with allergic skin rashes.
Hives
The medical term for hives is "urticaria." Hives are short-lived skin rashes that typically come and go within a 24-hour period, according to the Allergy and Asthma Foundation of America. The characteristic signs of hives include red, raised inflamed patches of skin. Hive are usually located around the face and neck, but can occur anywhere in the body. Hives can result from an allergic response to food, medication or other substances, but can also occur in response to stress, heat and pressure on the skin.
Contact Dermatitis
Contact dermatitis results when the skin comes in direct contact with an object to which the individual is sensitive. The symptoms of contact dermatitis can include inflammation and scaly, red rashes. The rash caused by poison ivy is one example of contact dermatitis. Blisters of the type that occur in reaction to poison ivy can occur in response to contact with other allergens as well, such as metals, cosmetics and plants.
Photocontact dermatitis is a type of contact dermatitis that occurs when the area of skin that has come in contact with the allergen is then exposed to the sun. It exhibits the same symptoms as other types of contact dermatitis, but is only caused when both factors, contact with the allergen and sun exposure, occur together, according to the Asthma and Allergy Foundation of America.
Eczema
The dry scaly bumps of eczema are another allergic skin reaction. Eczema is also referred to as atopic dermatitis. It is commonly found on the knees, elbows, scalp, back of the hands, and in infants on the cheeks. The itching caused by eczema can be extremely intense, and scratching the lesions can open them up and introduce bacteria to the area, resulting in infection. Eczema is often triggered by allergens but can also be caused by stress, overheating and exposure to skin irritants such as wool, according to the American Academy of Allergy, Asthma and Immunology.
Allergic rashes of the skin can be painful and aggravating. Fortunately, they are relieved once the allergen has been identified and removed from the individual's environment.
