Goat’s milk has always had the reputation in alternative circles of being healthier than cow’s milk. It is leaner, which may be an advantage for adults but not for children, who can handle the fat and need the calories. Other than that, its composition is largely the same. Goat’s milk is harder to find and more expensive. There is a vogue suggesting that newborns can be fed goat’s milk because of its chemical similarity to breast milk. This is not recommended, at least not for very young children. If you buy goat’s milk for an older child, buy the pasteurized kind. Fresh goat’s milk is associated with specific bacterial infections that could be harmful.
As for allergies, goat’s milk is not suitable if a child is allergic to cow’s milk, because of cross-reactivity.