Specific immunotherapy (SIT) is a treatment used to help people who suffer from allergies. An allergy is an overreaction by the immune system to substances like pollen that are harmless to the body, and specific immunotherapy is a technique of training the immune system to become less aggravated by a particular allergen. This method of reducing the severity of allergies requires the affected person to be exposed to small quantities of the allergen through injections or through oral drops. Specific immunotherapy is also known as hyposensitization or allergen-specific immunotherapy.
Allergies are abnormal responses to substances such as peanuts, dust and pollen. Some people suffer from allergic reactions to one or more of these substances that are so severe it impacts on the quality of life for the person. Asthma is one example of an allergy that is potentially life-threatening, and a condition called anaphylactic shock can also kill people with allergies to substances like shellfish or nuts. The exact way in which allergies work is all due to the components of the immune system reacting badly to allergens.
Normally the immune system is helpful in fighting infection, as the cells and the antibody molecules in the body recognize and destroy a variety of invading pathogens like bacteria or viruses. Generally, the antibodies and immune cells register the presence of an invader, and send signals to the body to help kill and break down the invader. These signals include molecules that act as instructions to produce swelling, redness and pain at the affected area.
When a person has an allergy, these signals produce symptoms that are not helpful to health, and indeed are detrimental to health. At the mild end of the scale, an allergy can produce symptoms like red eyes, an increase in tear production or skin rashes. Severe allergic reactions can cause the body's tissues to swell so much, or constrict the lungs, so that the person cannot breathe. Anaphylactic shock can also affect the ability of the heart to beat normally.
Although allergens produce undesirable effects in those affected by the allergies, scientists have figured out that actually presenting the immune system to the allergen can help train the immune system to respond in a more normal manner to the allergen. With specific immunotherapy, the exact allergens from the substance in question, such as proteins from peanuts, are packaged into a vaccine-like product. Typically, specific immunotherapy requires the allergen to be injected into the body, or absorbed into the body through liquid drops under the tongue.
Generally, the body adapts to a regular exposure to an allergen with a reduced level of immune response, as it has learned to deal with the allergen in a less over-the-top manner, so patients commonly have to have an extended course of specific immunotherapy over time. A risk of severe allergic reactions still exists with the immunotherapy allergens, and some people do not respond to the treatment. Some people, however, after a course of treatment, find that their allergies to a specific substance have disappeared.