Is it an allergy if my skin is itchy?

Since three weeks ago, small grain-like bumps have clustered together into round shapes, turned red, and become itchy.

So I scratched it, and it gradually increased one by one, now it appears sporadically on both arms.

I intentionally avoided scratching with my hand to prevent wounds, and instead used my palm to rub, which helped reduce the itchiness.

Eventually, the redness disappeared, leaving only clustered millet-sized bumps, and they didn't itch.

That state repeated 1 or 2 more times, and today it happened again, but the range has become a bit wider.

I don't know why it appears and disappears... I don't understand the cause of why this happens.

At first, I thought it was psoriasis, but it seems a bit different... Maybe it's an allergy...

I was planning to go to the dermatologist, but since the symptoms disappeared, I haven't gone yet because it's awkward to go.

I didn't have any particular skin itching, but maybe it's because my immune system has weakened... I'm still itchy now ㅠ.ㅠ