A COMPANY in Darlington has rediscovered an ancient Chinese formula for insect repellent.

Citrepel, produced by chemical design and development company Chemian, is based on a Chinese substance called quenling, which means "insect repellent" in Mandarin Chinese.

Chemian managing director Ian Dell said: "We took an enquiry for a material we had never heard of and spent the next six months trying to find out what it was. We discovered that lots of Chinese people knew what quenling was in principle but not in fact because most of the records had been lost during the Cultural Revolution."

The only information Mr Dell had was a scientific paper written in the 1970s, which contained a reference to quenling being extracted from eucalyptus oil.

After months of research, Chemian came up with the formula for Citrepel. Launched 18 months ago, it is sold mainly to other companies that make insect repellents.

There has been a lot of interest in the UK and the US, and Mr Dell hopes the company will soon crack the Australian market.

Citrepel is made in Cambridge and transported to Billingham, where it undergoes final modifications to enhance its citrus fragrance before being packaged and sold.