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.
Or the condom may have broken or fallen off during sex. A girl may be more than 24 hours late in taking the pill. The emergency contraceptive pill (or the morning after pill) is a hormone pill that can be taken up to three days (up to 72 hours) after having unprotected sex to prevent pregnancy. The sooner it is taken the more effective it is.