I have severe itching that extends near my testicles to my anus and it seems to be spreading and is blistered and red.

Hello,

what you are describing seems to be a fungal infection in the gluteal fold. It is a mild infection that can be treated with an over-the-counter cream

Get a cream for athlete's foot or vaginal infections: Canesten, Monistat, Micatin... Apply the cream 3 times a day until it is completely healed. It can take up to 3 weeks

To reduce the inflammation, burning and itching, the first few days you can apply a low strength cortisone cream, for example Hydrocortisone 1%, which is also available over the counter

If you do not see any improvement after 5 to 7 days of regular treatment, consult a doctor

Take care of yourself!