Depends on the type of house and sort of damp.
My house is currently suffering with bad condensation due to the damp cold conditions and the single skin solid brick walls making a cold surface for the air to condense onto.
problem with this is the natural yeast spores in the air growing in the damp conditions producing black mold (yup the dreaded....) I have also found some issues in the kitchen from the previous owner, they have papered over the air bricks, and the extractor hood above the hob is in "recirculation" configuration and vents humid cooking steam back into the kitchen. I'm sorting all that out next week.
There's a few systems that can combat this but the main issue is the moisture levels in the air, we now have 2 dehumidifiers running.
If it's rising damp you need a DPC specialist, plenty about.
Penetrating damp, you can DIY a few solutions for this.