Schmincke Oil Medium N

This product does not contain turpentine, and can therefore be suitable for artists with allergies.

From the Schmincke website:

A neutral, nearly non-yellowing, painting and thinning medium for oil colours. Suitable for all painting techniques except for early layers on absorbent undergrounds (not lean enough); has a low impact on drying time. For dilution, use terpin (max. 30%). Dosage: 10 to max. 20%. Contains: alkyd and acrylic resin, mineral spirit.