If your skin tends to be dry, reactive, or easily sensitized, approach this soap with caution initially. Birch tar has a strong cleansing action that may be too intense for some skin types.
For your first use, lather the soap and apply it to a small, non-sensitive test area (like your forearm) for just one wash. Rinse thoroughly and observe your skin's reaction over the next 24 hours. Look for signs of redness, tightness, itching, or noticeable irritation.
Only proceed to use it more widely if your test area shows no adverse reaction. Even then, many people use tar soap selectively on areas that tend to feel oilier or less fresh, rather than as an all-over body wash every day. As with any new cosmetic product, stop using it immediately if discomfort occurs. This product is not intended to diagnose, treat, or prevent any skin condition.