Mast cells. Mast cells and basophils are generally thought to be the major sources of histamine and can themselves be modulated by histamine as they express H 1, H 2 and H 4 receptors, although how this varies between different mast-cell types is not yet clear.
3. The pill is to be taken soon after unprotected sex. It should be taken preferably within 24 hours and before 72 hours or else the pill may turn useless. 4. I-pill checks pregnancy by preventing ovulation or fertilisation or implantation of the fertilised egg. 5. I-pill is 95 per cent effective if taken in time.
Take the pill as soon as possible after unprotected sex. The earlier you take the pill, the more effective it is. It can be taken up to 120 hours (five days) after having unprotected sex. It is a type of hormone which seems to work by stopping or delaying release of an egg (ovulation).