My helmet has an adjustable ratcheting system to fine tune the fit for big or small hair days. I wish my motorcycle helmets could adjust somehow as well.
If you have a helmet liner or sizing pads in the helmet, throw them in the washing machine and machine dry them too.
Old motorcycle trick after a haircut, or when the liner begins to pack out. It will plump right back up and take up the space nicely.
The ratchet adjustable helmet systems are nice for fine tuning, but they aren't usually as nice as a proper set of sized pads to really dial in the fit.