For my atopic dermatitis, trying to buy hygrometer, which type will be best?

Rapid capability: I have many in my home & office to keep the environmental humidity within range. There are many available that operate on button battery power & provide both a temperature & humidity reading. I prefer those with a digital read out. If you blow into the device it should show the increased humidity in your exhaled air within moments. The mechanical variety are too slow to be helpful.