Hi, I can understand your concern for red, swollen and tender butt crack. You have not told us your age and any other problem. This kind of infection of the skin is quite common in this hot weather and the further spread of infection to nearby of other parts. To prevent the further spread maintain good hygiene by taking two times bath, wearing cotton clothes and change of clothes two times. You can also use any good medicated antiperspirant powder. Stay away from hot and humid climate. You can use a mixed cream containing fluticasone and mupirocin cream locally over the affected areas. Do not try to scratch the area further as can cause secondary infection. You can take antihistamine like loratadine for two times a day. I advise you to take antibiotic tablets by mouth only under dermatological supervision. Take care.