I have two hanging lamps in my bathroom. I always used normal bulbs 40 Watt. Recently, I changed one bulb and put in an LED 40 Watt.
When I turn the switch on... I hear a HISSING NOISE coming from the LED bulb !
Is this dangerous and should I go back to the normal bulb.
Thanks

I hope you mean 40 watt equivalent, not 40 watt?

Yes. 40 watt equivalent.

Try the bulb in another socket elsewhere in the house.

A hissing sound is usually caused one of two things. The bulb is not screwed in all the way and you are hearing an electric arc. The other reason is the driver for the LED is not compatible with an old style dimmer. Some LED bulbs can be dimmed some can't.