There is a version of sunburn that happens to careless people, and there is a version that happens to careful ones. This note is about the second. It is a list of the sites that get missed, why they get missed, and what to do about each.
The underlying point is that sun protection is not really a product problem. It is a coverage problem, and coverage fails in the same places for everybody.
The scalp
The top of the head faces directly upwards at the point of maximum ultraviolet, and hair is not a uniform shield.
The parting
A parting is a line of exposed scalp, oriented perfectly for the sun. Anyone with a fixed parting takes a repeated, narrow dose along the same line for years, and it burns readily.
Thinning hair and shaved heads
The crown is the highest and most exposed point on the body. There is no ambiguity here: it needs covering or protecting.
Vented helmets
A cycling or climbing helmet is a grid, and ultraviolet passes through the vents. The result is a dappled pattern of burn on the crown, which is a reliable indication that the helmet was structural rather than protective. A thin cap underneath resolves it completely. See road cycling.
Wet hair
Hair flattened by water gives less cover than dry hair, which is one reason swimmers and surfers burn on the scalp.
What works: a hat, a cap, a helmet cover or a swim cap. Sunscreen on a scalp with hair is unpleasant and rarely applied properly, so textile is the practical answer for anyone with hair, and a genuine option rather than a fallback for anyone without.
The ears
The most consistently missed site on the body. Ears are three dimensional, they are behind the field of view when applying, and people apply to the face and stop at the jaw.
The tops of the ears and the outer rims take direct sun in almost every posture. The skin behind the ear and the earlobe take reflected ultraviolet on water and snow. A cap leaves all of it exposed, which is the argument for a brim or a legionnaire flap.
What works: making the ears a deliberate step rather than part of the face, and choosing a hat that covers them.
The back of the neck
Exposed by any forward leaning posture, which means cycling, running, paddling, walking with a pack, gardening and most manual work. Abraded by collars, pack straps and wetsuit seals. Invisible to the person applying.
What works: a collar, a neck flap or a buff. This is a textile site rather than a film site, because everything that touches it rubs.
The backs of the hands
Face upwards during almost every activity, washed repeatedly, wiped, gloved and ungloved, and applied to last if at all. On outdoor workers, cyclists, sailors and paddlers they accumulate an enormous amount of exposure. The wrist, in the band between a glove cuff and a sleeve, is a particular gap.
What works: a deliberate application at the end of every session, and gloves or sleeves where the activity permits.
The tops of the feet
The signature holiday and paddlesport burn. Feet are flat to the sky when sitting, lying or paddling, they are wet, they are in sandals with an exposure pattern that follows the straps, and they are the very last thing anybody applies to.
What works: including them by habit, and remembering that a sandal strap line burn is uncomfortable for a week.
The undersides
On water and snow, ultraviolet arrives from below. The underside of the chin, the underside of the nose, the inside of the arms and the eyelids all become exposed sites in those environments. Our note on reflected ultraviolet covers the mechanism, and our conditions files on ski touring and sailing cover the practice.
The lower lip
Faces upwards, thin, unpigmented, and constantly removed by eating, drinking, wiping and wind. Covered in our note on eyes and lips.
Why these sites and not others
Full body protection
What it certifies
Nothing specific. It is a descriptive phrase rather than a claim tied to a test method, and it describes an intention rather than a performance characteristic.
What it does not
It cannot certify coverage, because coverage is entirely determined by the person applying the product. Every study of application behaviour finds the same sites missed, and no formulation can put itself on the back of your own neck.
Three reasons recur.
You cannot see them. The back of the neck, the tops of the ears, the crown. People apply to what they can see in a mirror.
They feel unimportant. Feet, hands and ears do not feel like sunbathing surfaces, so they are not treated as such.
Something is assumed to cover them. Hair, a hat, a helmet, a sandal. Each of those covers less than it appears to.
A routine that catches them
Apply in a fixed order and finish each section before moving on:
- Face, including the nose and the area under the eyes.
- Ears, tops, rims and behind.
- Neck, front and back.
- Each arm in turn, ending at the back of the hand and the wrist.
- Shoulders and chest.
- Each leg in turn, ending at the top of the foot.
- Scalp, or a hat.
- Lips, with a product carrying a sun protection factor.
The bold items are the ones that get missed. If you only add those, you have addressed most of the sunburn that happens to careful people.
Why a mirror is a poor instrument
Almost everyone applies sun protection in front of a mirror, and a mirror shows you exactly one view: the front of your face, at eye level, with your head still. It shows you nothing about the tops of your ears, the back of your neck, the crown of your head, the backs of your hands as they face upwards, or the tops of your feet.
That single fact explains most of the list above. The sites that get missed are, almost without exception, the sites a mirror does not show. It is worth applying by touch and by sequence rather than by sight, which is why the fixed order below is more effective than trying to be thorough.
Backs, and the thirty second favour
The upper back is the largest single area most people cannot reach or see, and on swimmers, snorkellers and anyone in a vest it is among the most exposed. Asking someone to do your back is normal on a beach and somehow becomes unthinkable in a car park before a hill walk. It should not be. It takes half a minute and it covers an area no amount of contorting will reach properly.
Where nobody is available, the practical alternatives are a garment, which removes the problem entirely, or a long handled applicator, which exists and is more useful than it sounds for anyone regularly outdoors alone.
What is not verifiable
We publish no statistics about missed sites and cite no prevalence figures, because we have collected none. The list above comes from the mechanism, the geometry of the body and the consistent pattern described in public guidance from the health bodies. It does not need a number to be actionable.
The other reason to know the list
These are also the sites worth paying attention to when you check your skin, because they are where cumulative exposure concentrates. Our note on checking your skin sets out how, and the NHS is the right source for what to do about anything you find.