My toddler's insect bites leave dark marks on his legs. Does anybody know of an effective lightening topical cream, lotion, or anything?

Anything that can keep your baby's skin moisturized. For dark marks, we use either Sunflower Oil or Wonder Oil by Human Heart Nature. Very effective especially for my baby's occasional garters marks due to cloth diapers. Other moms swear by HHN's Rescue Balm. Photo credits to Human Heart Nature