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.
1 To use Seasonale as an Emergency Contraceptive, take all pills no more than 120 hours (five days) after unprotected sex. 2  It is most effective when taken within 72 hours (three days). 3  Dosage for emergency contraception: take four pink pills and, exactly 12 hours later, take another four pink pills.