I heard that if you eat something you're allergic to in small increments, you'll lose your allergies. Is this true?

I also wanted to know if this is true, or it's just a coincidence for my cousin, allergic kasi sya sa pagkain ng chicken, palagi syang tinutubuan ng mapupulang rashes, tapos, everyday, nag-iincorporate sya ng chicken sa meals nya pakonti konti, hindi na sya nagkakarashes.