Allergies that make people itch have the symptom but not the cause in common. Different types of allergens enter the body in different ways. Where contact with an allergen occurs often determines the site of the symptoms, reports the University of Maryland Medical Center.
Some people have multiple conditions with overlapping allergy symptoms that include tingling skin or itchy rashes. Itching can be a serious effect of an allergic reaction, because scratching and breaking the skin can lead to infection.
Contact Allergies
The list of substances that cause contact allergies is very long. Often, prolonged exposure to a substance sensitizes a person until a threshold is reached, and an allergic condition results. The Mayo Clinic notes that such allergies, called allergic contact dermatitis, are irreversible.
Allergens that can cause redness, itchy rashes, skin bumps and hives include: weeds such as poison ivy and poison oak; personal care and household items that contain detergents or fragrances, such as deodorant, soaps, cosmetics and solvents; preservatives such as formaldehyde; occupational dust, chemicals or metals; jewelry, rubber and latex; and some topical medicines, such as antibiotics and antiseptics.
Insect Venom Allergies
An insect sting allergy is a reaction to a chemical in the venom of a bee, wasp, hornet or fire ant. Because this substance enters the bloodstream, a systemic reaction involving the whole body can occur.
Allergy symptoms can include itching anywhere on the body or an itchy rash that forms at the sting site and spreads. Itching may precede or accompany anaphylaxis, a life-threatening reaction that affects respiratory and cardiovascular function, according to the Cleveland Clinic.
Hay Fever Allergies
Hay fever allergens, such as tree and grass pollens, contact the body through the mucous membranes of the eyes, nose and mouth. During an attack of hay fever, patients may have itching in the eyes, nose and throat.
Food or Drug Allergies
An allergic reaction to a food or drug, likewise, produces itching or tingling in the mouth. As the allergen is absorbed through digestion, a systemic reaction can take place. The University of Maryland Medical Center reports that an itchy rash can form anywhere on the body after eating a food or taking a drug.
