Several infectious skin diseases also cause a rash. These can be caused by a number of infections with bacteria or viruses, and infestations of mites within the skin. Some infectious skin diseases, such as scabies, are caused by mites that bore into the skin surface causing irritation and a localised rash.
Now, as for your question about when to start taking oral contraceptives, there's really no hard-and-fast rule about when to start taking birth control pills. Starting in the first few days of your cycle is the surest way to prevent inadvertently taking pills while you are pregnant.
If you are not breastfeeding, you may start taking birth control pills 3 weeks after you give birth. You may be able to take certain types of birth control pills if you are breastfeeding. These pills can be started from 6 weeks to 6 months after you give birth. Ask your caregiver for more information about when to start taking birth control pills after you give birth. You have forgotten to take a birth control pill.