Some of these chemicals are histamine, leukotrienes and prostaglandins, and they're what cause allergy symptoms. Researchers think that the tendency to develop allergies is genetic. People with allergies seem to produce more IgE than those who don't have allergies. Now my son has inherited my problems with allergies. Most are allergic to a combination of pollen, dust or animals.
Food allergies can happen very quickly.
Saff said that in some cases, the mere aroma of an offending food allergen can cause blood pressure to plummet, sending the allergic person into shock. Allergic reactions to animals are usually triggered by familiar domestic pets, such as dogs and cats. Allergens can be in the dander or fur of many animals and in the proteins of their saliva. The most common allergen, however, is household dust, which is generally made up of fibers from fabrics, bacteria and bits of plants and insects. Most dust also contains tiny, microscopic insects called dust mites, which live in carpets, upholstered furniture and bedding.