Amine hydrofluorides of the general formula (I): R--N(CH.sub.2 CH.sub.2 OH).sub.2.HF (I) In which R is a straight-chain hydrocarbon residue having 10 to 20 carbon atoms exhibit antibacterial and caries-prophylactic activity and can be prepared in high purity. The amine hydrofluorides of the formula (I) can be formulated, optionally in combination with tin fluoride, into oral hygiene compositions such as toothpastes, mouthwashes or chewable tablets.