Dribbling from teething will cause the perfect environment for chronic bacterial infection.
You may be able to get a prescription for Fucidin ointment, not the cream though as it tends to make the tissue soggy since it’s water based. The ointment is oil based so can act as a barrier.
I think you can request a prescription from the pharmacist, since it is a form of impetigo. It’s in its early stages so you need to act quickly to stop it spreading.
Clean and dry the area thoroughly then apply the ointment using a clean cotton bud. You should use the smallest smear to create a thin, barely there layer. If you smear a huge blob it has an unpleasant taste and traps food and saliva.
Don't rub it in, sort of paint it on and extend it a down into the chin area, basically the area saliva from dribbling collects. It waterproofs the skin stopping it from becoming too soggy.
Although it’s not impetigo it’s similar in that bacteria are living and growing in the soggy cracked upper layers of skin. It’s important to dry the skin so the ointment can adhehe. If you put it on while it’s wet you trap the moisture in encouraging further growth.
It can be due to candida from the mouth so it may be worth trying nappy cream or a barrier cream you use, but again a greasy ointment is more effective than an aqueous cream.
You will have to keep on top of it while they are dribbling.
You could also try a very old remedy which is to feed them live yoghurt daily. It helps to keep the candida levels down in the mouth.
In adults we only really see it in denture wearers. Poor denture cleaning leads to an overgrowth of candida. Treating the source of infection is often more successful than treating the end result. But it has a similar cause in children when their faces are a bit creased up around the mouth.
It’s perfectly normal to have candida in the mouth but when teething children tend to mouth breath encouraging higher levels. Also they continually have their fingers and everything else stuffed in their mouth. At 18mnths they can be prone to overgrowth of candida since their oral microbiome, needed for healthy mouth ( similar to gut biome) is still not fully mature.