Allergic contact dermatitis, drug rash and swimmer's itch are examples of allergic skin rashes, according to Mayo Clinic. The allergens associated with contact dermatitis and drug rash vary.
Contact dermatitis occurs when individuals touch substances to which they are allergic, states Mayo Clinic. The rashes are red, bumpy and itchy. Sometimes, blisters form. Examples of common rash-causing allergens are latex rubber, nickel and poison ivy. Symptoms often do not appear the first time individuals handle the substances.
In some cases, a drug rash develops when a patient is allergic to a medication, Mayo Clinic reports. It is also a general side effect of certain drugs. The rash typically shows up during the first week the medicine is taken. Random red spots appear first, and then they multiply, extending over much of the body. The rash often does not disappear until days or weeks after the patient stops taking the drug.
Swimmer's itch, or cercarial dermatitis, is a rash is caused by an allergic reaction to a water parasite, explains Mayo Clinic. The organism tunnels into the upper layer of skin, creating a reaction of tiny red bumps or blisters. Home treatments of lotions and soothing baths help individuals tolerate symptoms until they disappear in about one week. Each exposure to the parasite increases the severity of the rash.