If your skin tends to react to active ingredients, it is advisable to apply a small amount of the balm to a limited area — for example, the inside of the wrist or the crook of the elbow — before using it regularly. Wait 24 hours and assess the reaction: redness, itching or a burning sensation is a sign that the product in this form is not right for you.
Several ingredients deserve particular attention. Birch tar is a traditional but fairly active ingredient that can cause irritation in some people on first contact. Salicylic acid gently exfoliates rough skin cells, but on very thin or sensitive skin it may be felt as a slight tingling. Lanolin in the base sometimes causes a reaction in people with a known sensitivity to it.
If you are using topical medicines or other products with a pronounced effect on the same areas, it is worth consulting a specialist before using them together, as the effects of the active ingredients may add up. If you have a chronic skin condition, or are pregnant or breastfeeding, it is also advisable to consult a doctor first.