Allergies are responses mounted by the immune system to a particular food, inhalant (airborne substance), or chemical. In popular terminology, the terms “allergies” and “sensitivities” are often used to mean the same thing, although many sensitivities are not true allergies.
The term “sensitivity” is general and may include true allergies, reactions that do not affect the immune system (and therefore are not technically allergies), and reactions for which the cause has yet to be determined.
Some non-allergic types of sensitivity are called intolerances and may be caused by toxins, enzyme inadequacies, drug-like chemical reactions, psychological associations, and other mechanisms. Examples of well-understood intolerances are lactose intolerance and phenylketonuria.
Environmental sensitivity or intolerance are terms sometimes used for reactions to chemicals found either indoors or outdoors in food, water, medications, cosmetics, perfumes, textiles, building materials, and plastics.
Detecting allergies and other sensitivities and then eliminating or reducing exposure to the sources is often a time-consuming and challenging task that is difficult to undertake without the assistance of an expert.
What are the symptoms of allergies?
Common symptoms may include itchy, watery eyes; sneezing; headache; fatigue; postnasal drip; runny, stuffy, or itchy nose; sore throat; dark circles under the eyes; an itchy feeling in the mouth or throat; abdominal pain; diarrhoea; and the appearance of an itchy, red skin rash.
Life-threatening allergic reactions—most commonly to peanuts, nuts, shellfish, and some drugs—are uncommon. When they do occur, initial symptoms may include trouble breathing and difficulty swallowing.
Dietary changes that may be helpful.
A low-allergen diet, also known as an elimination diet or a hypoallergenic diet is often recommended to people with suspected food allergies to find out if avoiding foods that commonly trigger allergies will provide relief from symptoms.
This diet eliminates foods and food additives considered to be common allergens, such as wheat, dairy, eggs, corn, soy, citrus fruits, nuts, peanuts, tomatoes, food coloring and preservatives, coffee, and chocolate. Some popular books offer guidance to people who want to attempt this type of diet.
The low-allergen diet is not a treatment for people with food allergies, however. Rather, it is a diagnostic tool used to help discover which foods a person is sensitive to. It is maintained only until a reaction to a food or foods has been diagnosed or ruled out.
Once food reactions have been identified, only those foods that are causing a reaction are subsequently avoided; all other foods that had previously been eaten are once again added to the diet.
While individual recommendations regarding how long a low-allergen diet should be adhered to vary from five days to three weeks, many nutritionally oriented doctors believe that a two-week trial is generally sufficient for the purpose of diagnosing food reactions.
Strict avoidance of allergenic foods for a period of time (usually months or years) sometimes results in the foods no longer causing allergic reactions.121 Restrictive elimination diets and food reintroduction should be supervised by a qualified healthcare professional.
Lifestyle changes that may be helpful.
People with inhalant allergies are often advised to reduce exposure to common household allergens like dust, mold, and animal dander, in the hope that this will reduce symptoms even if other, non-household allergens cannot be avoided.
Strategies include removing carpets, frequent cleaning, and vacuuming, using special air filters in the home heating system, choosing an allergen-reducing bed and pillow coverings, and limiting household pets’ access to sleeping areas.
Nutritional supplements that may be helpful.
Probiotics may be important in the control of food allergies because of their ability to improve digestion, by helping the intestinal tract control the absorption of food allergens and/or by changing immune system responses to foods.
One group of researchers has reported using probiotics to successfully treat infants with food allergies in two trials: a double-blind trial using Lactobacillus GG bacteria in infant formula, and a preliminary trial giving the same bacteria to nursing mothers.
Probiotics may also be important in non-allergy types of food intolerance caused by imbalances in the normal intestinal flora. According to one theory, allergies are triggered by partially undigested protein. Proteolytic enzymes may reduce allergy symptoms by further breaking down undigested protein to sizes that are too small to cause allergic reactions.
Preliminary human evidence supports this theory.
Hydrochloric acid secreted by the stomach also helps the digestion of protein, and preliminary research suggests that some people with allergies may not produce adequate amounts of stomach acid. However, no controlled trials have investigated the use of enzyme supplements to improve digestion as a treatment for food allergies.
Many of the effects of allergic reactions are caused by the release of histamine, which is the reason antihistamine medication is often used by allergy sufferers.
Some natural substances, such as vitamin C and flavonoids, including quercetin, have demonstrated antihistamine effects in a test tube, animal, and other preliminary studies. However, no research has investigated whether these substances can specifically reduce allergic reactions in humans.