Allergic symptoms are caused by the release of active substances from cells following the reaction of the body’s immune defense mechanism to the allergen. These substances are histamine, serotonin, a slow-reacting substance, and bradykinin. The liberation of histamine has two important physiological actions. First, it causes the small blood vessels to leak so that fluid is poured out into the tissues (the effect may be so pronounced that the blood pressure may fall and unconsciousness ensue; this is called anaphylactic shock). Secondly, it causes spasm of smooth muscle, for example, of the lungs.
Food allergy symptoms: The first symptom of an allergic reaction to food is very often itching and swelling in the mouth, tongue and throat. You may also get some more symptoms like: skin reactions, such as swelling and itching, eczema and flushing, vomiting and diarrhea, dizziness etc. An allergic reaction to food usually happens quickly or typically within an hour of eating the food and sometimes almost immediately.
Wheat allergy symptoms: Allergic reactions to wheat may be caused by eating of wheat-containing foods or by inhalation of flour containing wheat. An allergic reaction to wheat usually begins within minutes or a few hours after eating or inhaling wheat. The more common symptoms involve the skin, gastrointestinal tract and the respiratory tract. The most usual symptoms include: hives, eczema, angioedema, abdominal cramps, nausea, vomiting, oral allergy syndromes, asthma or allergic rhinitis.
Mold allergy symptoms: The most common symptoms of the Allergies caused due to molds are: sneezing, runny nose, blocked nose, coughing, postnasal drip, itching eyes-nose & throat, dark circles under the eyes, nose rubbing, continual upward nose rubbing, watering eyes, conjunctivitis, red-rimmed eyes, swollen eyes and crushing of eyelids.
While diagnosing allergies, the history of symptoms is very important especially when the symptoms alter according to the time of the day, season, exposure to pets and other potential allergens and diet changes. Severe reactions have often been noticed abruptly after exposures like eating nuts or getting stung.