Itching is a widespread allergy symptom of sensitivity to allergens that you touch, breathe in or ingest. Skin tingling or an itchy rash often occur with allergic reactions. Itching can be a warning sign that precedes more serious symptoms, such as anaphylaxis -- a total-body metabolic disturbance. Itchy rashes usually fade within a few weeks, unless an underlying skin condition is present.
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Allergic rhinitis, commonly known as hay fever, is a seasonal allergy that can cause itching. This allergic reaction to airborne pollen grains affects the mucous membranes of the eyes, nose and mouth. After inhaling an allergen such as grass or tree pollen, itchy eyes, nose or throat may be the first allergy symptoms.
Food or Drug Allergy
In addition to causing digestive tract symptoms, allergic reactions to foods or drugs may produce itching. Eye itching and an itchy rash or hives elsewhere on the body may result from an adverse reaction to a food or medication. Peanuts, milk and antibiotics are known sources of allergies in some people. Itching symptoms, often accompanied by swelling, may be immediate or arise within an hour or two.
Bees, wasps, hornets and fire ants all transfer their venom to humans during a sting. An allergic reaction to this substance can induce itching on any area of the body, not just the sting site. Allergy symptoms following insect stings may also include respiratory problems.
An itchy rash often appears in spots where the body has come into contact with certain plants, such as poison ivy, poison oak or poison sumac. Itching can be intense and persistent, possibly accompanied by hives and pain. Severe reactions may cause skin to bubble and blister, raising the risk for infections from scratching and breaking the skin. People should wash clothing or outdoor gear after contact to avoid transferring the plant's resin and creating a chain reaction of allergic irritation.
Other Contact Allergies
Poison ivy allergy is just one of many forms of allergic contact dermatitis, caused by touching the plant, that can cause itching. An itchy rash may be an allergy symptom of contact with rubber, latex and certain chemicals in sensitive individuals. Some metals, such as nickel, in jewelry can cause adverse reactions in certain individuals. Contact allergies can occur with cleaning products, cosmetics, perfumes and fabrics among the allergies that can cause itching.