Shampoos often contain a lot of chemicals, scents and other potential irritants. These elements may make shampoo smell good and can lead to silky hair, but they also can cause allergic reactions in some people. Signs of an allergic reaction to shampoo include itching, blotchy skin, flaky scalp and swelling. It is important for people to remember that an allergic reaction to shampoo does not always show signs immediately after a shower. Symptoms can sometimes take more than 24 hours to begin.

One sign of an allergic reaction to shampoo is excessive itching that may be accompanied by red blotches or a rash. The itching may be limited to a person's scalp, but it also can involve areas the shampoo touched as it ran down the body during a shower, including the back, breasts, arms, stomach and even genitals. If hives are present with the itching, a person should take an over-the-counter antihistamine. Calamine lotion can be used to sooth itching skin and prevent scratching.

A flaky or peeling scalp is another common sign of an allergic reaction to shampoo. A person who believes his or her flaky scalp is a result of using a specific shampoo should discard the shampoo immediately. A person also may find relief by skipping washing his or her hair for a few days and using cool water instead of hot during showers. If the peeling does not seem to be clearing up on its own, a person should contact his or her doctor for prescription shampoo. When a flaking scalp is the only symptom present, a doctor also can confirm that it is the result of an allergic reaction to shampoo and is not being caused by an underlying medical condition.

An allergic reaction to shampoo also can cause swelling to the body. Patients can use cool compresses or over-the-counter antihistamines to reduce minor swelling. When severe swelling is present or if the swelling is causing a person's throat to close, he or she should go immediately to the emergency room for professional medical treatment.

A person who has had an allergic reaction to shampoo should use preventive measures to avoid future occurrences. Hypoallergenic shampoos are available to cater to the needs of people with allergies or sensitive skin. Purchasing baby shampoo is another option for people with allergy sensitivities, because baby shampoo typically contains fewer irritants. If no over-the-counter shampoo seems to do the trick, a patient should turn to his or her doctor for a prescription solution.