Tanning bed rays can and do go through a towel.
Towels do not block or stop the UV rays from towels so you still get the UV rays on your skin or eyes when using a towel in the tanning bed.
Many Salons will offer a towel to clients tanning in their tanning beds to protect their face but don't be fooled as the towels do nothing to protect you from the harmful UV rays of a tanning bed.
You must also wear special tanning glasses to protect your eyes from the harmful UV rays in the tanning bed.
Closing your eyes is not enough to block the UV rays from your eyes.
Using a tanning bed even once could possibly give you cancer.
However it would be a rare chance that you would get cancer just from using a tanning bed only once.
Usually it takes several tanning sessions in a tanning bed over a few years or longer to develop cancer from the tanning bed.
Many people use tanning beds for years and never develop cancer such as skin cancer but some people develop cancer after a few tanning sessions in a tanning bed.
Tanning in a tanning bed is never really a healthy thing to do because the UV rays from the tanning bed are more dangerous to your skin than tanning in the natural sun.
Tanning in the natural sun gives you Vitamins which can be healthy and it's less harmful to tan naturally using the sunlight than to tan in a tanning bed.