Histamines are chemicals that are released from basophils and mast cells -- cells in the immune system -- in response to the presence of an allergen (see ref 1). Common allergens include pet dander, latex, mold, insect bites or stings, pollen, dust, and certain foods or medications (see ref 2). These chemicals elicit an immune response that causes hives, sneezing, allergic asthma, and a more serious reaction called anaphylaxis (see ref 1).
Hives or rashes can occur in response to allergens such as food or medication (see ref 1). These can manifest as red, swollen, itchy bumps on the skin (see ref 1).
Itching of the nose, which causes sneezing, can also be a result of histamine release in response to an allergen (see ref 2).
Another effect of histamine is allergic asthma, or asthma-like symptoms in the presence of an allergen (see ref 1). Inhaled allergens -- such as pollen, pet danger, and dust -- cause the release of the chemical, thereby causing airway obstruction and inflammation (see ref 1). This is characterized by coughing or wheezing, chest tightness, and shortness of breath (see ref 1). Allergic asthma is a serious condition and must be addressed by a physician, immediately.
Anaphylaxis is a rare but serious, and potentially fatal, reaction to an allergen. The histamine that is released causes a systemic or total body reaction (see ref 3). Any type of allergen can trigger anaphylaxis; however, food is the most common trigger (see ref 3.) The signs and symptoms of this serious allergic reaction can include: wheezing; shortness of breath; hives, swelling and flushing; swelling of the tongue, throat and nose; dizziness; nausea and stomach cramping; and a significant drop in blood pressure (see ref 3). It is of vital importance that you seek medical assistance, immediately, at the nearest hospital if you believe you are having an anaphylactic reaction (see ref 3).