Hi hun,
Just to let you know I asked the hairdresser and they said it is safe to have foils as the bleach is not touching the scalp and being absorbed. It is when you are having the chemicals directly put onto your scalp that it is dangerous as it can be absorbed through the scalp.

Just a warning if you do go (I did and still do) the chemicals in the hairdressers can be a little bit more overwhelming now that your nose is more sensitive to smells. I found it not to be as relaxing as it normally is going to the hairdressers.