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.
EllaOne is another type of emergency contraceptive pill. It can be taken up to 120 hours (five days) after having unprotected sex, but is only available on prescription from a doctor if you are 18 or over. If you take it, you can't breastfeed for 36 hours afterwards.