Babies under 1 year old should not be given honey because honey can contain spores of a bacterium called Clostridium botulinum. These spores can cause infant botulism, a serious and potentially life-threatening illness where the bacteria grow in a baby's immature digestive system and release toxins that affect nerve function, leading to muscle weakness, paralysis, and breathing difficulties. Babies' digestive and immune systems are not mature enough to handle these spores before their first birthday, but older children and adults can safely consume honey because their bodies can prevent the spores from growing and producing toxins.

Symptoms of infant botulism in babies may include poor sucking, weak cry, constipation, decreased muscle tone (floppiness), difficulty swallowing, drooping eyelids, and respiratory problems.

For these reasons, health authorities like the American Academy of Pediatrics, CDC, and WHO recommend not giving any honey or foods containing honey to infants until they are over 12 months old.