The scent of birch tar is indeed very pronounced, reminiscent of a campfire, smoked wood, or tar. It is a defining characteristic of the ingredient and is noticeably stronger than most essential oils or fragrance oils used in cosmetics. When you open the bottle, the aroma will be immediately apparent. During use, even when diluted in a shampoo or soap, the smoky character will be present during application.
Regarding lingering scent: if used in a rinse-off product like shampoo or body wash and you follow with your regular conditioner or body rinse, most of the direct smoky odor will be washed away. However, a subtle, woody-resinous note may remain on the skin or hair for a short while, especially if used in higher concentrations or in leave-on products like balms. This lingering trace typically fades within a few hours. To manage the scent, it's advisable to use this product as part of an evening routine rather than right before social events, and ensure you rinse thoroughly. Pairing it with lightly scented but non-irritating follow-up products can help. It's important to choose this product specifically for its functional, traditional character, not for a perfumed experience.
Given its potency, always start with the smallest recommended amount in your dilution to see how you tolerate both its effect and its aroma before considering any increase.