Itching is defined as the sensation that causes the desire to scratch and produces moderate to severe discomfort. Itching is one of the most common skin symptoms that bothers our patients. The medical word for itch is pruritus. Itching is most often, but not always, related to the normal skin defense of histamine release. Histamine is the “itch chemical ” produced by our body to let us know something is wrong and it alerting you to an allergen. Histamine causes redness, swelling, and itching. For example, the “welt” that develops after a mosquito bite. That is why “antihistamines” are sometimes recommended to treat itch.
Itching is not always due to an allergy. Dry skin, skin product ingredients, friction (like scratching!) can trigger itch. Some skin conditions are extremely itchy, and can make a patient have sleepless nights! Examples of itchy skin problems are atopic eczema, contact dermatitis (like poison ivy), chicken pox, “hives” (urticaria), and scabies. Usually the provider can identify the pattern of a rash to make a specific diagnosis of what kind of itchy rash a patient has.
Itching when there are no visible rashes or spots is a lot trickier to figure out. Medications or internal problems ( like thyroid, kidney or liver disease) can cause generalized itching.
Contact dermatitis is a skin reaction caused by a substance or physical insult from the outside “in contact” with the skin surface. There are 2 main types of contact dermatitis:
Irritant Contact Dermatitis
Contact Dermatitis Irritation is direct outer skin damage, which can occur from excessive dryness, wetness, soap, friction, rubbing of the skin, bleach, alcohol, or solvents touching the skin surface. Any of these, or a combination, can trigger redness, stinging, and itching. The immune system is not a trigger for this type of skin reaction, and the diagnosis is based on exposure history and appearance of the skin. Examples of irritant contact dermatitis are “winter dry skin”, chapped lips, hand eczema from frequent handwashing, or chafing. Some types of diaper rash are due to irritation.
Allergic Contact Dermatitis
An otherwise harmless substance in contact with the skin can trigger an immune or “allergic” reaction, causing a red, usually VERY itchy dermatitis. It does not have to be anything “new” in contact with the skin, and can occur for the first time at any age. In a sense, your body’s immune system is doing its job to alert you that something is in contact with the skin! Even ingredients in baby products can cause reactions of this type, but only in very few individuals. Common examples of allergic contact dermatitis are poison ivy or oak dermatitis and nickel reactions causing a rash at sites of metal jewelry touching the skin. Allergic contact dermatitis can occur to gloves, skin product ingredients, fragrances and “botanicals”, chemicals used in the workplace, and even topical medications. If the provider suspects an allergic contact dermatitis, a type of allergy testing called “patch testing” may be ordered to help figure this out.