Based on the symptoms (red bumps on the side, intense itching, and inflammation), there are several possibilities:

Shingles (Herpes Zoster): It usually appears as a band or stripe on only one side of the body and burns or itches intensely.
Dermatitis: An allergic reaction to a soap, lotion, or laundry detergent.
Bites: If the bumps follow a straight line, they could be bedbug bites.

What to do?
See a doctor: If it is shingles, it is urgent to start treatment within the first 72 hours.
Do not self-medicate: Applying random over-the-counter creams can make the inflammation worse.
Do not scratch!: Scratching can cause a severe bacterial infection from the fingernails.

In summary: Don’t take any chances; it is best to have a doctor check it out soon so it doesn’t turn into a bigger problem.