Secret Horse Adieu Tiques

Ceramic stone (composed solely of clay fired at high temperature and bacteria, i.e. living organisms)
100% natural, it contains no chemical substances
The stone simply disrupts the tick's receptors.
The pearl sends a signal to the ticks. This signal will generate genes in the parasite's receptors, preventing it from detecting your horse, so it won't even have time to settle on your 4-legged friend.