There can be various kinds of allergies such as dust, pollen, medicines, food, insect, viruses or bacterial allergy. The allergic reaction may be a small skin rash on one spot or all over the body. The reaction happens when substances called antigen trigger immune system of the body. The function of immune system is to protect the body from harmful substances like bacteria. When the immune system senses harmful substances, it is called hypersensitivity that is also known as allergic reaction.

Generally, allergic reaction is not dangerous to life but it may cause end of life in severe cases. One of extensive form of allergy is anaphylaxis that appears sudden and leads to shock, problem in breathing or unconsciousness. It happens because of sudden dilation of large blood vessels. The blood pressure often drops under this condition, and consequently, may cause cardiac arrest or death.

The most common symptoms include skin redness, itching, swelling, blistering, weeping, crushing and rash. Symptoms may involve coughing, shortness of breath, swelling of face, swelling of eyelids and lips, tongue or throat swelling, sneezing, red or watery eyes, stomach pain, vomiting and diarrhea.

The cause of allergic reaction is a chemical process inside the body. The immune system contains white blood cells producing antibodies. When antigen exposes the body, it causes reaction.

You must go and consult your doctor for any allergic reaction. As a stop-gap, to food allergy, a person should avoid the food that caused problem. For seasonal allergies, necessary precautions should be made at the right time. Similarly, in case of a skin allergy, the particular area should be treated with ice or cold water.