I got resin veneers in my upper teeth last summer and since then i've presented a constant burning sensation in my tongue. daktarin oral gel, oral wound support gel, and difflam been tried as per gp's advice, nothing has worked. may it be an allergy?

It may, but it may also be coincidence. There is a condition called "burning mouth syndrome". Here's more info, more than I can fit in 400 characters: https://www.mayoclinic.org/diseases-conditions/burning-mouth-syndrome/symptoms-causes/syc-20350911

Dr Rhoads and another doctor agreed

Resin veneers are plastic unlike porcelain laminates. The burning sensation could be from the plastic content of the veneers or the cement or both .Since nothing works than in invest in porcelain veneers but if you eat spicy foods stop or cut down to see if burning sensation goes away if not than porcelain it is.

Very unlikely that a resin veneer would be causing a burning sensation on your tongue. could be an irritation from an edge your tongue is finding at night.