After the verb Help, you can have an infinitive form of verb. The infinitive form can be either a to-infinitive or a bare infinitive. That is actually optional. Mostly in conversation or informal English, the to is often left out.

Examples –

He helps him (to) learn Russian.

Alex helped a blind man (to) cross the road.

N.B So a bare infinitive as well as an infinitive with to is both acceptable after help. But it’s observed that in BrE the to-infinitive form dominates, though bare infinitive also occurs in BrE. On the other hand in AmE a bare infinitive is preferable. When there is a repetition of to (a pattern of to + help + to + verb) as in this sentence – she allowed Pearl to help her to stack up her hair – a bare infinitive is generally occurs. Another place where bare infinitive is preferred is when there is an intervening noun phrase as in help people break the cycle of poverty. Bryan A. Garner writes the better usage is to use bare infinitive after help, while Pam Peter says the preference of to-infinitive in BrE is because of their conservatism but this practice is changing.