Question:

Does using vibrators on the penis head permanently desensitise the penis head?

A: Generally, no. 

Using a vibrator on the head of the penis does not permanently desensitise it. Using strong, or even prolonged, vibration in that area can sometimes cause temporary numbness or reduced sensitivity immediately afterwards, just like if you were to hold a very strong vibration in your hands and they go slightly tingly and numb. Still, sensation should return once the nerves have had time to recover.

If you find you need increasingly intense vibration to feel pleasure, it can help to vary the intensity, placement and type of stimulation you use rather than relying on one sensation every time. Think of it as giving your body a broader "menu" of stimulation to respond to so it doesn't become accustomed to the same thing. 

If numbness or reduced sensation persists when you're not using a vibrator, or you notice a significant or sudden change in penile sensation, it's worth speaking to a Doctor or sexual-health professional to rule out other causes