What lacquer thinners can do your insides?

If you drink it, you'll probably die. Inhaling it will cause brain damage, and so will getting it on your skin.

Lacquer thinners can damage the liver and kidney and can also impact your central nervous system (brain). Skin irritation will result from substantial or prolonged skin contact, and some may be absorbed through the skin and contribute to those systemic effects.

Any effect requires that there have been a high enough exposure, and the worst effects usually require the greatest expsoure. Many people are exposed and experience adverse effects but do not die. However, death can result from a big enough exposure.