Shingles is a common viral infection of the nerves[i]. Although it emerges as painful blisters on the skin, it is not a skin disorder, but a neurological disorder that affects the skin.
Let’s talk about Chicken Pox
We can’t speak about shingles without mentioning chickenpox since you can’t get shingles unless you have had chickenpox at some stage, even if it was decades before. Shingles are the secondary infection that arises from the varicella-zoster virus or VZV, the same virus that causes the primary infection called chickenpox.
Before the introduction of the chickenpox vaccine in 1995, the vast majority of children caught chickenpox before the age of 6 and acquired life-long immunity to it. In healthy children, the infection normally lasts for 2 to 3 weeks and causes a mild fever and a rash of red spots accompanied by small itchy blisters that spread to the face, head, and trunk.
Chickenpox is highly contagious from about 2 days before the rash and blisters appear, being spread by saliva, mucus, and airborne particles from coughing and sneezing. Once the blisters emerge, it can also be spread by direct contact with the blisters and by indirect contact with the clothing of an infected person. The blisters take about 5 days to dry up and crust over, by which time they are no longer infectious.
After the disappearance of the rash, it’s not the end of the story. The virus doesn’t ever leave the body but instead becomes dormant. It takes up residence in the dorsal root ganglia and hangs out there in an inactivated state until something wakes it up.
The dorsal root ganglia are clusters of neurons. These neurons are the first ones of the sensory pathway and connect to the channel carrying sensation from the body to the brain via the central nervous system.
This feature of being able to establish a latent infection is one common to the herpes virus family, to which the varicella-zoster virus belongs. If and when the virus becomes reactivated, it is known as herpes zoster and expresses as the thoroughly unpleasant condition known as shingles.
Like chickenpox, shingles can also cause fever, malaise, rash, and blisters but rather than just being itchy, it can be excruciating. In fact, the first sign of shingles is usually unexplained pain or weird tingling and itching on one side of the body. The pain from nerve inflammation most often precedes the development of a blistering rash. The blisters themselves can also be painful due to the replication of the virus in the skin leading to more inflammation.
Because shingles is a neurological disorder, both the pain and the rash are almost always unilateral [ii] (affecting only one side of the body). They are described as being dermatomal. A dermatome is an area of skin supplied by a single spinal nerve, so the infected nerve will dictate what path the pain follows along that particular nerve root to the skin.
The most common sites for shingles to appear are the torso and chest but it can appear just about anywhere, including on the face, near the eyes and ears, and on the arms and legs.
Is Shingles Contagious?
Yes, no, sort of. You can’t get shingles from someone with shingles but you can get chickenpox from them. “People who have never had chickenpox before can be infected with the varicella-zoster virus by coming into contact with the fluid from inside shingles blisters. In this case, the infection causes chickenpox and not shingles.” [iii]