Fading away

I've noticed that sometimes my dog's nose and lips can become less brown. It's usually when she's about to come into season. Is it an old wives tale or could this be a sign of a lack of iron?
An old breeder friend says to give her kelp - but where do you get it? Someone else recommended Brewer's Yeast. But how much and how often? (She's a Springer Spaniel)
Should I go to my vet and get her checked out? Could this be a symptom of something more serious? I read on a forum that autoimmune can be linked to fading pigment.
Sarah Stevens

This loss of pigment is indeed related to the bitch’s season. It is a sign that accumulated wastes (toxins) are being eliminated. This is a “good thing” although it would be better if the excess of toxin were not there in the first place. It is difficult to advise as you do not say what you are feeding but a better quality diet or a reduced amount of the existing food (or both) should help. It is not a deficiency of iron or anything else.
There are other circumstances in which this type of pigment change occurs. At Burns we occasionally see changes in pigmentation of the nose or the skin when dogs change to Burns food. White dogs turn pink; black dogs turn brown. The first time it happened I was alarmed that the food might be deficient in zinc. As I’ve already said, it’s a cleansing process, a discharge of toxins and is a sign that the health of the body is improving. Similar changes occur in some dogs when they moult which is itself a cleansing process.
John Burns BVMS MRCVS, Burns Pet Nutrition