Tanning bed rash??

I’ll start by saying I have tanned for over 10 years of my life on and off but mostly on. I’ve never had any issues tanning. This last year my parents bought a tanning bed and I have started using it more frequently, last week I tanned 4 days in a row, by day 4 I got this super itchy rash that feels like pins poking the area itchy. It’s right at the top of my butt crack where most of my weight sits when laying on my back. I stopped tanning and treated it with hydrocortisone cream and it went away. Thought I was in the clear after a week of no tanning and went tanning again tonight, I couldn’t even finish tanning because I felt the rash coming back. It’s raised from my skin, super itchy, pins and needle itchy, and is hot. I have no idea what’s causing it? Could it be the cleaner? But then why isn’t it anywhere else on my body? I don’t think it’s the lotion because I don’t always use lotion anyways when I’m feeling lazy. I’ve tanned for years and am just now having this problem. Can anyone help?? It hurts!!