Caulking, also called a sealant, is used to seal cracks. If you need to paint caulking, choose one that specifically says “may be painted”. Many silicones cannot be painted.
Caulking is flammable; it contains solvents. Some caulking has no solvents, but it still off-gasses chemicals, so use it with ventilation and caution if you react to chemicals. Hybrid caulking is a blend of polyurethane and silicone and is often the best choice for prople experiencing Multiple Chemical Sensitivity (MCS).