Babies are not allowed in the pool for obvious reasons and while you may see some parents allowing their little babies a few minutes in the water, this is quite prohibited. However, it boils down to how old the baby is; if they are a few months to 1-2 years you should not allow them in the hot tub.
Some of the reasons why it is ill-advised to let a baby into a hot tub include:
They are susceptible to overheating
A hot tub is often heated to 104 degrees and babies have thin skins which mean their bodies will heat up pretty quick. Even if they are old enough not to get jerked by the heat, they should not be let there for more than five minutes. You can reduce the temperature to around 98 degrees to allow them to have more soaking time (no more than 15 minutes).
(See the best baby bathtubs for your choice)
Babies are lacking in control
An adult would know what to do when they slip and fall in the water. Things like not breathing inside water, finding something to grip quickly and regain posture are not automatic responses for babies. In simple terms, babies do not have enough control to be inside a hot tub and you must never let go if you insist they soak for a minute or two.
Babies should not go into hot tubs just to make sure no accidents happen especially since one small occurrence may lead to the closure of your spa for a long time. Only those who can stand up without being fully covered by the water may get the opportunity for a few minutes. A good alternative is to choose spas that have jump seats. These seats ensure your baby is only covered by water from the waist downwards but even then, never let them stay in hot water for long.