Final answer:
Lavender essential oil could be a safe and effective addition to a tonic for a pregnant client with acne due to its anti-inflammatory and antimicrobial properties, but a healthcare professional should be consulted beforehand.
Step-by-step explanation:
When considering an essential oil to add to a tonic for a pregnant client experiencing acne, it is crucial to choose oils that are safe for pregnancy. An appropriate option would be lavender essential oil, known for its therapeutic properties that can help soothe acne-prone skin without being harsh or over-drying.
Lavender oil has anti-inflammatory and antimicrobial properties, which may assist in reducing acne inflammation and controlling bacteria on the skin. It is also calming and can help with stress, which can sometimes exacerbate acne. However, as with all treatments during pregnancy, it is vital to consult with a healthcare professional before using essential oils to ensure safety for both mother and child.