We endevour to remove all stains, but if the stain has already caused permanent damage to the fibres, this may not be possible. With any stain, we recommend you do not use household cleaners on it prior to professional help as a combination of the product and scrubbing/agitation can cause damage.
Think of a radish and a carrot. A radish can be white on the inside and pink on the outside, this is how we describe a carpet stain that has not been scrubbed or worked on and the stain remains on top of the fibres. A carrot is orange all the way through, so could have already caused permanent damage to the fibres, permanently stained carpet.
The type of carpet also plays a part in stains being ‘removeable’. A wool carpet for example can easily absorb stains as it has ‘fish scales’, where as a polypropylene carpet is more likely to repel stains as it is more plastic based.