Found these red bites in a straight line on my brother's neck this morning

Aside from the visual pattern of bites, other symptoms can help confirm a bed bug issue. Itching is a common symptom, and excessive scratching can lead to secondary infections. Some individuals may experience allergic reactions to the bites, resulting in swelling, blistering, or even hives.
In rare cases, individuals may develop insomnia or anxiety due to the psychological stress of knowing they are being bitten during sleep. Monitoring for these symptoms can provide additional clues and help determine the need for medical intervention.
4. Immediate First Aid: How to Soothe the Itch and Reduce Swelling Safely
For immediate relief, wash the affected area with soap and water to reduce the risk of infection. Applying a cold compress can help reduce swelling and soothe itching. Over-the-counter antihistamines or anti-itch creams containing hydrocortisone can provide additional relief.
Encourage your brother to avoid scratching the bites, as this can exacerbate irritation and lead to infection. Keeping nails trimmed and wearing gloves at night can help minimize damage from scratching.
5. When to See a Doctor or Urgent Care About These Bites
Most bed bug bites can be managed at home; however, if your brother experiences severe symptoms such as a widespread rash, difficulty breathing, or signs of an allergic reaction, seek medical attention immediately. Persistent or infected bites that do not improve with home treatment also warrant a visit to a healthcare provider.
Documenting the progression of the bites with photographs can be helpful for medical professionals in assessing the situation and providing appropriate care.
6. Step‑By‑Step Guide to Checking the Bed, Mattress, and Room for Bed Bugs 

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