Can you wear tampons back to back?

You can, however it is best to alternate with pads as often as possible.

Tampons encourage bacterial growth while effecting vaginal pH and preventing the vagina from cleaning-out bacteria - tampons also dry-out vaginal tissues causing damage. Although you're removing the bulk of the bacteria when you remove the tampon itself the fact is that some will remain in the vagina, particularly within fibres left behind by the tampon, so inserting another tampon is preventing the vagina from cleaning-out this bacteria and the stray fibres. By wearing a pad after a tampon you allow vaginal cleaning, the vaginal pH can re-adjust, and it gives the vagina a chance to heal.