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.
A progestin-only contraceptive is one kind of birth control pill. It is often called the mini-pill.. Regular birth control pills have 2 female hormones: estrogen and progestin (a synthetic version of the naturally-occurring hormone progesterone).o contraceptive method is perfect, even when you use it correctly. 2 or 3 of every 100 women who use the progestin-only pill correctly could still get pregnant. This risk of pregnancy is almost the same as the risk with regular birth control pills.