Coconut allergy is relatively rare.

http://www.allergycapital.com.au/Pages/coconut.html

What you had was probably candida die off. Was itching throat the only symptom you had? Even if you had a rash, a rash could be the result of candida die off. Do you have allergies to other foods? Did you use virgin or extra virgin coconut oil? Many websites advise avoiding coconut oil which is made from copra(dried coconut), and only use virgin or extra virgin coconut oil.