An allergy is defined as a physical reaction that occurs in persons who are sensitive to certain substances. A substance that is harmless to a nonallergic person may cause mild to extremely severe symptoms in an allergic person. Common forms of allergy include asthma, hay fever, and a year-round nasal allergy called perennial allergic rhinitis. Others are eczema, hives, allergic headaches, and allergic digestive disturbances. A substance that causes an allergy is called an allergen. The allergens that cause most asthma, hay fever, and other respiratory allergies include house dust, mold spores, pollen, and the dandruff or hair of household pets (dander). Foods can also cause allergic reactions. These foods include chocolate, milk, eggs, wheat, peanuts and certain seafoods, especially shellfish. Additional details: Gallagher, Joan S. "Allergy." World Book Online Reference Center. 2004. World Book, Inc. 24 Apr. 2004. <http://www.aolsvc.worldbook.aol.com/wb/Article?id=ar013900>.

I'll give a few possible remedies for allergies further on. Bob has got some weird behavior...he tries to invalidate many, many of my answers...and rates me down...as if I care about ratings. I care about relaying valuable information which many times is not mainstream nor supplied by vested interests. Find out for yourself what is true for you from your own investigation and direct observation and tests. There is some useful information already provided in some of the other answers. Here is some more data. Allergies or sensitivities can be caused by a variety of different things which often vary from individual to individual. Here are just a few examples of what could cause allergic reactions. It could be a single criteria or a combination of different things which affect the individual. This answer doesn't cover every possibility. Some allergies are actually psychosomatic, caused by unknown previous incidents held in the mind which are affecting a person without that individual's awareness. A person is unknowingly restimulated by the current environment. The past incidents being restimulated "act" to influence the individual without the individual being aware of "why". If the individual knew "why", the condition would no longer exist. "The proof is in the pudding" when these hidden mental image pictures and content are viewed in an organized fashion resulting in the allergy vanishing. To express this in other terms, a person can be unknowingly affected by hypnotic "commands" and doesn't recognize exactly what they are because they are hidden from conscious view. Many people recognize the mild forms. One example: if they get sick from drinking too much tequila and thereafter feel nauseated from the thought of drinking a shot. But if, for example, a person was knocked out or injured from a car wreck and had the left-over taste of pickles from an earlier hamburger in their mouth...later on in life when just tasting a hamburger with wheat bread...a person has a reaction to the wheat bread. Pickles equal hamburger equal wheat equal pending pain in the body. It doesn't add up logically, but the restimulation of one item can have these odd ties to something completely different. In fact, all sorts of aberrations with an individual can occur from the same sort of hidden force and command held in the mind without the person's awareness of what is going on. This is a very brief explanation. The point is that some allergies are actually psychosomatic. Sometimes allergies are caused because of build-up of other toxins within a body's system. These other toxins make the body respond oddly to other potential irritants. There can be all kinds of different toxins which invade a person's system from a variety of sources including foods, cosmetics, soaps, shampoos, toothpaste, cleaning products, plastics, herbicides, pesticides, etc. Metals (aluminum is very common), solvents, a whole host of chemicals, aflotoxins, can easily be absorbed into the body through eating, just plain skin contact, or breathing. While the body works hard to expel these poisons, they will collect in the tissues and fats and organs of the body (and often "recirculate" through the body and redeposit themselves). It is commonly underestimated by the general public on the extent of pollutants absorbed by the body from a variety of products and environmental factors. Again, I want to say: the amount of absorbed toxins and their role in inhibiting the body functions can be dramatic, yet it is not generally confronted by the broad public. -[Just one anecdote: Chemicals from teflon can now be found in the systems of most every American. Dupont had a less toxic residue type teflon formula since 1996, but intentionally did not put it on the market. In fact, in 1984 ( 20 years ago) Dupont secretly tested drinking water in towns near their teflon plant and found that they were poisoning the town by dumping thousands of pounds of waste into the river. This information is from their own internal memos which went on to say the inference that "the liability is already there, so what the hell !" ...and then they actually almost tripled the amount of waste over the following years. The horror stories and crimes of Dow and Dupont and Monsanto and Eli Lilly and Scotts and others go on and on.] - Anyway, these toxins within the body can cause a variety of different symptoms, one of which is allergies. [The symptoms caused by toxins go on for pages and pages, and include headaches, easily catching colds and the flu and other common bugs, fatigue, nausea and gastrointestional difficulties, endocrine and hormone problems (problems with conception and sperm counts are among the many), liver or kidney or other organ problems, muscular or heart difficulties, nervousness, memory loss, irritability, depression, misemotional responses, dispersal of attention, eye problems, the whole array of breathing difficulties, etc., and of course, the predisposition to most cancers.] The remedy is to remove the source of the toxic exposure and/or remove the toxins which have accumulated within the body. Often a person is relieved of allergy symptoms, just from removing toxins which have been held in the body. Another influencing factor on allergies is nutrition. A well balanced diet and healthy regimen goes a long ways towards handling allergies. If the body is not in a healthy state, it responds oddly to other potential irritants. There is a lot of information found elsewhere on this site about nutrition and supplements, such as essential fatty acids which assist in relieving allergies. You can search the subject, or click on my name or the name of others to gain more data. There are also cleansing herbs which help the organs of the body and the system in general to remove or handle the antagonisms of allergy restimulations. A simple thing such as Vitamin C or taking some apple cider vinegar "with the mother" or eating a lime may alleviate some symptoms of allergies. Even something like Bee Pollen, taken on a gradient could help. The proper homepathic remedy when found will, of course, handle the difficulty...but sometimes it is not the correct remedy, or the symptom is not the result of something which can be remedied by homeopathy. Then you will receive no real benefit to handling the allergy from that particular homeopathic remedy, because it was the wrong remedy. Many foods are missing vital nutritional components now-a-days. Processing and our agricultural system have robbed us of some of the benefits of whole foods. See my article on fertilizers to learn more (click on my name or do a search). You can also write me. If a person is lacking in certain nutritional components, they can respond badly to some substances. There are supplements and herbs which can help to reduce allergic reactions. Some good information is in a variety of different areas on this site. A sidenote here is that there are parasitic organisms. They can affect the body directly or indirectly, and also internally or externally. As just one example, there are many mites or microbes which feed on dead skin or thrive in the presence of skin and hair. Often, their excrement is toxic and causes all kinds of reactions when an individual comes in contact with it. There are even paper mites and molds which can aggravate symptoms. When in environment heavy with these (such as an old records building or perhaps your cat-friendly associates), a simple thing that I found to temporarily combat some of these toxins was to put a drop or two of lemon or lime juice in my nose. A longterm handle on a facility or home might be an ion filter, which I had applied to a warehouse I once had. Enzymes could help handle some of the problems associated with allergens. The website www.getipm.com/ has some links which will lead you toward some products. Also, there are ads on pages of this website that sometimes offer ethical products. Internal parasites affect the majority of the population. They can cause a full variety of symptoms within a body. Handling parasites and toxins along with a healthy, balanced diet full of variety can go a long way towards eliminating allergies. Some people have had great success in handling allergies and asthma with oil of oregano (the type of oregano plant that is natively wild in the Mediterranean). By researching and experimenting with a variety of handlings, you may be able to come across something successful which works for you if you suffer from allergies. A good nutritious diet goes a long ways. Eat right. Variety. Leafy green vegs etc. I should mention that the probiotics of fresh vegetables alone can help a person. In other words, when eating fresh greens, you can obtain beneficial microbes in a way that is similar to yogurt's beneficial microbes. The more beneficial microbes (and nutrients), the healthier the body's system. A healthy natural system is less prone to being compromised with difficulties such as allergies or ailments.

Scientists do not know what causes a peanut allergy—or any allergy for that matter—but there is evidence of a predisposition when one or both parents of a child has allergies. However, scientists and doctors understand the causes of an allergic reaction to peanuts, or more specifically, an allergic reaction to at least seven of the proteins found in peanuts. Allergic people come into contact with these proteins through one of three general means: direct contact, cross-contact, and through the air (by inhaling them). http://www.peanutallergy.com/causes.html