Cross-sensitivity to phenothiazine antipsychotics such as promethazine, chlorpromazine, endothiazine, and trifluoperazine. Erythromycin is cross-allergic to macrolides such as madicamycin, crossamycin, and spiramycin. Tetracycline is cross-allergic to methomycin and doxycycline. Gentamicin has cross-allergy with aminoglycoside antibiotics such as kanamycin, butamycin, tobramycin, etc. It is also important to note that to avoid cross-allergy to drugs, in addition to avoiding drugs with similar chemical structures, drugs containing the same serum protein preparation should be avoided. For example, patients allergic to tetanus antitoxin injections should also not use rabies serum injections in the future, because both of these drugs mentioned above, contain serum proteins from horses. Most of the allergies that occur in patients to this type of medication are to the animal horse serum proteins in this type of medication. In addition to the two aspects mentioned above, people who have had a drug allergy should also avoid using compounded preparations containing the same ingredients as the first allergic drug.