If your skin is easily reactive, the first step is to patch test. Apply a small amount of lather to the inside of your forearm, rinse it off, and watch the area for a day or two. If redness, itching, or a burning feeling appears, do not use the soap on larger areas.
This soap contains lanolin, a waxy substance traditionally used in skincare. Lanolin is well tolerated by most people, but some are sensitive to it. If you know you have a lanolin allergy, or if you have reacted to wool-based products in the past, avoid this soap. The product notes also mention fragrance, so if you are sensitive to fragrance, patch test before regular use.
When you do use the soap, avoid the eye area. If it gets into your eyes, rinse with plenty of clean water. Stop using the product if irritation appears. If you have a chronic skin condition, are pregnant or breastfeeding, or are on medication, consult a specialist before using a new cleansing product. This soap is a cosmetic product for cleansing and skin comfort; it is not intended to diagnose, treat, or prevent any disease.