According to the Wikipedia, Allergy is a disorder (or improper reaction) of the immune system often also referred to as atopy. An allergy can be in simple terms described as the reaction of the body's defense mechanism to an allergen and may cause reactions like sneezing, watery eyes, itchy rashes or swelling of the lips and tongue. The allergen or substance that causes allergy usually contains a protein. Some foods which produce excess heat in the system like prawns, eggs, meat etc may cause allergy to some. However, there are non-protein allergens which may cause an allergic response once they bind with protein in the human body like penicillin, sulpha, aspirin etc. Some of the common allergic disorders are eczema, drug rashes, headache, hay fever and bronchial asthma.

Allergy is one of the top ten reasons why an individual may visit doctors. An allergy may occur in any age. Many associate hereditary as one of the reasons leading to allergy. Unhygienic conditions and Pollutions are pointed out as another reason causing allergies. Other factors that may be contributing include diet, exposure to chemicals and carpeted housing. Mostly when the allergens causing the allergy is known it is advised to avoid the allergen altogether which always might not be possible. However, Ayurveda and Homeopathy has some good treatments for allergy.

Astrologists associate allergies with the presence of Mars in the Horoscope. An allergy can be caused when the allergens are taken by an individual who has Mars positioned in the 1^st, 4^th, 7^th, 8^th or 12^th houses in the Birth Chart due to excessive heat created in the body. A person having Mars in those houses should take adequate precautions. Gem Therapy recommends the usage of Cold Stones to avert such health conditions. Some stones which can be worn include Moonstone, Emerald and Yellow Sapphire which can make the body cool.