If your kids don’t want to take their prescription medicine, there might be a good reason.

According to one study, “The rejection of unpalatable medications is a reflection of the child’s basic biology. From an evolutionary perspective, the senses that evaluate what is put into the mouth have likely evolved to reject that which is harmful and seek out that which is beneficial.”

In non-scientist-speak: if a medicine smells or tastes bad, it’s normal for a child’s senses to tell their brain, “Don’t eat this, it could hurt you!” This survival mechanism is even displayed in newborn babies; researchers found that infants’ facial reactions suggest they dislike bitter tastes and prefer sweet ones.

Even if it makes sense, evolutionarily speaking, this reaction can be frustrating for parents and ultimately could keep children from getting the treatments they need.

If your child refuses to take a bad-tasting liquid medication, ask your pharmacist if it can be flavored. Many pharmacies can add flavors like chocolate, vanilla, a variety of fruit flavors and more to help make the medication more tolerable.

Some pharmacies charge an additional small fee for added flavoring — but it might be well worth the extra couple of dollars if it means your child gets the treatment they need with fewer fights.