Does head lice repellent have a use by date?

My Sister has head lice, and i have this head lice repellent spray, I've lost the cap and i'm not sure if it had a use by date.. it's a leave in spray by the way, it's been in our bathroom for ages and it looks like this ..http://www.amazon.co.uk/Natural-Head-Lice-Repellent/dp/B0014QUO6O/ref=sr_1_3?ie=UTF8&qid=1309531749&sr=8-3 .. should i use it in her hair?