Cycle helmet for a 10 month old?

[HenriettaPepperpot]

We've recently acquired mountain bikes and I'd like to start cycling with our 10-month-old. (Haven't yet plucked up courage to cycle with him around town, though would like to do so at some point). Does anyone know if babies this age should wear cycle helmets, and if so are there any recommended brands? Have seen some on Amazon, but not sure if they would fit him. I will have to measure his head.

[StuckUpTheFarawayTree]

Decathlon have some. They fit my 10 month old and she's quite petite.