Allergic reactions usually happen within a few minutes or a few hours after being exposed to the substance or food that you are allergic to. The symptoms can show up immediately in several cases- if it is an allergic reaction to dust, pollen or some food when the body's immune system starts the immediate defence mechanism by throwing up the symptoms. The immune system releases a substance called histamine which shows up as these reactions like sneezing, skin rashes, headache, running nose, nausea and so on. In some people the reaction can be immediate and severe; whereas in others it can be delayed and mild. Some life-threatening allergic reactions need immediate emergency treatment too.

Some allergic reactions can bring about shortness of breath, palpitations of the heart and the person need medical attention immediately. People who have an intolerance to certain foods can have difficulty in digesting the food, and as a result symptoms like nausea, headache, bloating, gas can occur which leads to the development of an ulcer.

In some people, the symptoms are present throughout the year but in some others, the symptoms can be severe and the suffering very high, like in the case of Asthma patients who suffer during winter and rainy season but are quite alright during summer.

A family history of allergies is also a known factor, which may pass down the generations.

Symptoms of Allergy can be various and can be listed as below:

Sometimes obesity and hypertension are also the outcome of long tenure allergic suffering.

Diseases identified are many and can be listed out as below: