I have always had good nails, but in the past couple of weeks I have developed horizontal ridges that have emerged from under every cuticle. I was very ill with pneumonia last month — could this have anything to do with it?

A thorough doctor will always glance at a patient’s nails during an examination as they can provide clues to a number of underlying problems. The changes you describe are probably beau’s lines — horizontal ridges that run across the width of all your nails caused by a temporary disturbance in growth.

The formation and growth of new nail is very sensitive to external factors including pregnancy, the weather, age, stress and illness. Nails tend to grow quicker when we are younger, pregnant or during the warm summer months. Stress and illness, particularly infections such as pneumonia, tend to inhibit growth and affect the laying down of new nail so that you are left with a temporary deformity that moves up the nail as it grows.

White flecks are another common change in the nail, and one that is often wrongly associated with an underlying vitamin or mineral deficiency. While a poor intake of zinc can sometimes cause flecking, the most common cause is trauma to the delicate nail fold under the cuticle — typically after knocks and bangs in people who work with their hands.

Other changes worth looking out for include spoon shaped nails (iron deficiency), fragile, crumbling nails (thyroid trouble) and dark purplish longitudinal streaks under the nail (heart trouble).

But perhaps most worrying of all is the change known as clubbing where there is loss of the natural angle between the nail and the cuticle. Clubbing can be normal in some people but if it is a recent change it may indicate a serious underlying illness including cirrhosis of the liver and lung cancer. The simplest way to check for clubbing is to hold your finger horizontally in front of you so you are looking at the nail side on – it should rise slightly as it leaves the cuticle and heads towards the fingertip.

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