What should you know about huge bed bug bites?

A bite may start as a small red spot and become a broad, raised, itchy area. Several marks can appear in a line or cluster on skin exposed during sleep, although the pattern is not proof of the cause. Some people develop delayed swelling or blisters, while others have little reaction. Scratching can break the skin and allow a secondary infection. Bed bugs live in the surrounding environment, so new marks may continue until bedding, furniture, and nearby hiding places are assessed and treated.

Wash the area gently, apply a cool compress, and keep fingernails short. Avoid squeezing blisters or applying irritating household products. A clinician or pharmacist can advise whether an oral antihistamine, such as [Antihistamine Treatment](/treatments/medical-dermatology/oral-antihistamine-therapy/), suits your symptoms. A short course of [Topical Corticosteroids](/treatments/medical-dermatology/topical-corticosteroids/) may be considered for inflammation when medically appropriate. Launder bedding using the hottest safe setting, inspect mattress seams, and arrange professional pest control when an infestation is suspected.

Arrange medical advice if swelling is extensive, lesions are painful, blisters are widespread, or itching prevents sleep. Seek prompt care for increasing warmth, pus, spreading redness, fever, facial swelling, trouble breathing, or dizziness. These features can indicate infection or a significant allergic reaction and should not be judged by the size of the bite alone.

Could this be a bite reaction, infection, or another rash? What can I use safely for the itch, and how long should I use it? Do any medicines or health conditions change my treatment options? What signs mean I should return urgently?