What Causes Strong Ammonia Smell From Hair?

I have been diagnosed as perimenopausal. I am 42 years old and have had a partial hysterectomy. Still have ovaries. In an effort to get the migraines under control, my doctor prescribed a hormone patch. Vivelle dot. It is the smallest doseage offered. It helped the migraines and am ecstatic about that. However, I now have a strong ammonia smell when I wash my hair and I can smell it even when it's dry! Could this be a side effect to the patch, or is it something different?