Pyrethrin Shampoo precautions What should I know regarding pregnancy, nursing and administering Pyrethrin Shampoo to children or the elderly?If you are: Pregnant: FDB Only When Necessary: NO HUMAN PREG DATA AVAILABLE. CDC RECOMMENDED TREATMENT FOR LICE IN PREGNANCY. Nursing: No Known Risk: INSUFF DATA AVAILABLE. CDC RECOMMENDED TREATMENT FOR LICE IN LACTATING WOMEN. Giving Pyrethrin Shampoo to a child under 12: management or monitoring precaution: Not recommended age < 2 years. Consult clinician.