When the substance enters the body, the body produces many antibodies in the blood to attack it. The antibodies then bind to a kind of white blood cell called mast cells. This binding causes the release of histamine, a chemical in the body which causes the uncomfortable, yet familiar hay fever symptoms. If hay fever develops in the spring, it's usually due to tree pollen. If it develops in the summer, grass and weed pollen are probably to blame.
Many people also develop hay fever in response to mold, dust mites, animal hair, etc.
Taking care to avoid these substances can go a long way in relieving allergy symptoms. Remedies that have been proven useful for allergies include Nettle Leaf, Vitamin C, Quercetin, and air ionizers. Quercetin belongs to a class of water-soluble plant coloring agents called bioflavonoids . Quercetin is often recommended as a treatment for allergies and asthma. A study of the herb nettle leaf was published in the journal Planta Medica .