I used to have blonde foils, then when there was so much blonde that it had taken over, I started having full head bleach as it was cheaper. It is addictive though because i think the roots are more noticeable and I felt I had to get it bleached all the time.
I think maybe when I was having highlights it was a high-lift tint which is less damaging, but when I had full head it was stronger stuff? My head did tingle and itch quite a lot with this but it ususally wore off when they washed it off. Honestly, the warm water on my head after bleach was such an amazing feeling of relief!!
Maybe your scalp is sensitive and you have had a bad reaction to it if it was still hurting after? I think they are supposed to do patch tests with any colour (I have never been offered one at any hairdressers though!).
Now I am growing out my full head bleach and just have foil highlights every now and again through the top as it was quite damaging over time, as you always get a bit of overlap between the new and old bleach when they apply it which weakens the hair and makes it prone to breakage. Although I have to admit to doing a few home applications which isnt the best idea! I would say if you do have it done again, try somewhere else and mention the previous experience as they may have used a stronger peroxide to get a faster result? (I'm not a colour technician though, just semi-educated guessing
)
Personally I have to break a full head bleach addiction (I'm not even kidding!!) in order to get my hair back to something like healthy again, so my advice would be if you were fine with foils before, try to grit your teeth through the drastic roots stage and stick with foils going forward xx