What causes bumps in the whites of eyes?

It depends on the size and color of the bumps. If the bumps are a clear to very light yellow in color, likely, the bumps are what are called pinguecula and are caused by allergies and sensitivity to sunlight. They are not harmful, but may make contact lens use a little uncomfortable at times. If the bumps are brown or black in color, that's usually just pigment... Either way, there is generally no cause for alarm unless the bumps get so large that you feel they're impairing your vision... that however is pretty unlikely. If you have dry or itchy eyes, there are a number of lubricating drops you can purchase over the counter - but... to fully put your mind at ease, I'd say the best solutionwould be is to see a Therapeutic Optometrist so they can give a full & thourough examination of the eyes and check those spots for any irregularities that might night have been addressed in this forum.

Hope that helped some!Cindy