Why patterns are unreliable
Bed bugs may feed more than once, several insects may feed close together and reactions may appear after a delay. The familiar “line of three” is not a diagnostic rule.
Basic self-care
NHS guidance says bites usually clear within about a week. Keep the area clean, avoid scratching and ask a pharmacist about symptom relief if needed.
When to seek medical help
Seek medical advice when pain, swelling or itching remains severe, when redness spreads or when signs suggest infection. Call emergency services for symptoms of a severe allergic reaction.
What to inspect next
Use a torch around mattress piping, bed-frame joints, the headboard and nearby furniture. Look for a specimen or multiple physical signs rather than repeatedly photographing the skin.
Limits and sources
This page supports triage, not diagnosis. Health wording follows current NHS guidance. Identification logic uses visible anatomy, movement and harbourage evidence; an intact specimen reviewed by a competent expert remains stronger.