Please follow this advice to best safeguard your artworks future.

Avoid hanging your painting directly over a radiator or fire, or anywhere particularly prone to damp or large variations in temperatures. 

Remove dust from your painting regularly to avoid it building up. Dust can contain certain acids which can erode or dry out the artwork. You can periodically remove dust from the oil painting with a soft brush or lint cloth. Don’t use feather dusters or dust cloths as they may scratch the painting surface. Don’t use a damp cloth or cleaning chemicals.

Aerosols and fine mist cleaning products should not be used near a painting. If you do use them, then spray them on a rag away from the painting, rather than spraying directly onto nearby surfaces.

Your painting has had a coat of varnish on top of the oil paint. This Varnish will help to protect from dust and pollution reaching the surface of the paint and damaging it. This creates a barrier to prevent removal of paint/colour when cleaning. If you ever need to have your painting professionally cleaned, then the varnish can be removed and replaced without disturbing the paint.

I use a Gamblin Gamvar Picture Varnish in gloss and you can add a new varnish over the current varnish without any need to remove it first.