How can I relieve itchiness on my neck?

The description of your rashes seems like hives. That being said, it is safer to consult a doctor to confirm the diagnosis of hives. If it is hives, both classes of oral medications: 1) anti-histamines such as cetirizine, telecast etc and 2) a short course of low dose oral prednisolone (steroid) should be prescribed by your doctor for quick and effective recovery. Topical steroid medications will be ineffective. Calamine lotion can help with relieving itch but it does not help with controlling the underlying inflammatory response.

Insect bite reactions are due to hypersensitivity response of the body to the insect bites. The area of the bites gets progressively redder,inflamed and itchy and the inflammation response can be very intense and severe at times, even leading to the development of blisters. Bed bug, sandflies and fleas are some common causes of insect bite reactions but it is often difficult to tell the exact insect that caused the bite from looking at the skin lesions. Insect bite reactions often require the use of topical steroid creams to settle the inflammation.