A: Most bites will heal within one to two weeks of appearing and not cause any long-term problems. Those with stronger sensitivities to insect bites may take up to three weeks or longer to heal. A: According to the Centers for Disease Control,it can take up to 14 days for a bite to appear. Some people may not notice bites at all, while others may see signs of a bite within hours. A: Bed bug bites are often mistaken for mosquito or flea bites.