Allergies occur when an immune system that is hyper sensitive reacts to a common or unusual substance (also called allergens). In some people, allergies are hereditary but one can develop allergies at any time in his or her life. A person might be allergic to such allergens as chemical toxins, food, dust, animal hair, pollen or parasites.
Allergies can irritate us no end. With symptoms like a runny nose, sneezing, itching to even asthma at times, allergies can make us miserable to say the least. If you have an allergy, you could be suffering from a cold, and in extreme cases, asthma and breathing difficulties might crop up. Add to that aches and pains, irregular heart beat and gastrointestinal problems, and your whole system might go for a toss.