An allergen is a type of antigen that produces an abnormally vigorous immune response in which the immune system fights off a perceived threat that would otherwise be harmless to the body.Such reactions are called allergies.hen an allergen enters the body of an individual that is predisposed to allergies, it triggers an immune reaction and the production of antibodies. These allergen antibodies migrate to mast cells lining the nose, eyes and lungs.
Progestins are synthetic progestogens, medications that have effects similar to those of progesterone. The two most common uses of progestins are for hormonal contraception (either alone or with an estrogen), and to prevent endometrial hyperplasia from unopposed estrogen in hormone replacement therapy.
Some women choose to take a progestin-only pill. Called the mini-pill, progestin-only pills allow women to avoid some of the worst side effects of estrogen, while improving regular menstrual cycles and preventing pregnancy.irth control: Oral contraceptives typically contain estrogen and progestin. Combination pills suppress ovulation (the release of an egg) each month. The progestin in these pills also reduces the risk of pregnancy by altering the mucus in your cervix, making it harder for the sperm to move and connect with an egg.