It is POSSIBLE to be allergic to synthetic hair!
According to this Post on BlackGirlLongHair.com,
” There is an alkaline base coated on synthetic hair which leads to allergic reactions in most people”. To Treat this situation it is advised to rinse your hair with Apple Cider Vinegar.
Please read: http://blackgirllonghair.com/2013/10/true-life-my-scalp-is-too-bougie-for-synthetic-hair/
it’s possible to be allergic to synthetic hair. as for me I am not allergic . I only get the blisters due to very tight hair either at the nape of the hair or in front. this is worth knowing