Ay, ringworm sa ganyang edad is tricky talaga! I'd really suggest checking with your baby's doctor first before trying anything, kahit gentle products like Bioderm, mas safe kung may go-signal from pedia kasi depende sa severity at location din. A few of my mum friends had the same worry, and their doctors prescribed specific creams or antifungal treatments na safe for babies that age, so better to get professional advice para sure na okay for your 7-month-old.