Hair gel permissible

If the gel which you are using contains intoxicating alcohol, then it is unlawful to use them (as wine is impure according to the opinion of scholars). It is unlawful for the person to use impure things except in urgent necessity and there is no necessity in this case. On the other hand, if alcohol has disappeared totally through the process of manufacturing and no longer intoxicates as it has changed into a different thing then, it becomes lawful to use it. The prayer of the person putting on perfumes containing intoxicating things is not valid unless the impurity is removed.

according to my knowledge being a science student-

The ethyl alcohol or ethanol is the only alcohol which is Haram because it causes intoxication. Ethyl alcohol is obtained from fermentation of sugar by yeast cells. Synthetic ethyl alcohol is obtained from ethylene gas and both are Haram because both cause intoxication.

Not all alcohols are Haram because they do not cause intoxication. These are fatty alcohols, sugar alcohols. The fatty alcohols are obtained from fat (they are Haram if they obtained from pork fat and if they obtained from vegetable fat then they are Halal) but not from fermentation of sugar in fruits such as grape and dates. Sugar alcohols are neither sugar nor alcohol and they are obtained from fruit tree, and plant sources. Sugar alcohols are Halal ingredients.

I would finally conclude by saying plz tell me the kind of alcohol in the ingredients of your hairgel ..so that I can help you out whether that alcohol causes intoxication or not..:)

and ALLAH knows the best...!!