Turtle skin problems: normal shedding, fungus and water quality

Quick answer

Turtles do not get fleas and they do not itch the way a mammal does. When an owner describes a turtle as itchy, what they have usually seen is one of four things: normal skin shedding, a fungal or bacterial infection of the skin, an irritation caused by water quality, or a rubbing behaviour that is not about the skin at all.

Telling those apart is mostly a matter of looking at the material itself. Normal shed skin is thin, translucent and comes away in sheets, leaving healthy skin underneath. A water mould infection is opaque, white or grey, cotton-like, sticks to the skin, and usually has reddened tissue beneath it. Redness without any covering, particularly on the underside and limbs, points at water quality or at a bacterial infection that has become systemic.

Examine a turtle out of the water in good light. Skin problems that are invisible under water are obvious once the animal is dry.

• Turtles have no fleas, mites or lice in normal captive conditions, and flea products must never be used on them.
• Wispy translucent material in the water is usually normal shed skin.
• White, fuzzy, adherent patches with red skin underneath are an infection and need a vet.
• The single most important treatment for most turtle skin disease is a basking site the animal can dry out completely on.
• Red patches on the plastron and limbs with a lethargic turtle is a systemic emergency, not a skin complaint.

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Reddened patches on the plastron and limbs in a lethargic turtle can mean septicaemia.

Septicaemic cutaneous ulcerative disease is a bacterial infection that spreads into the bloodstream. The signs are pink or red blotches and pinpoint haemorrhages on the underside of the shell and on the skin, ulcers, lethargy, refusal to eat, and sometimes limb weakness. It usually arises in poor water quality and it is fatal without prompt treatment. It is not something to manage with water changes and a salt bath. If your turtle has red areas on the plastron and is not behaving normally, that is a same-day appointment with a reptile vet.
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Decide in 60 seconds

Normal shedding, and why it looks alarming

Aquatic turtles renew their skin continuously. Small, thin, almost transparent sheets lift from the neck, the legs and the tail and float away, and in a tank with good lighting they are very visible. Owners often see this for the first time and assume the turtle is falling apart.

Normal shed has a reliable set of features. It is translucent rather than opaque. It comes away in sheets or flaps rather than tufts. It has no thickness to it. The skin underneath is normal in colour, without redness or swelling. There is no smell, and the turtle behaves entirely normally.

Shedding increases during periods of rapid growth, after a temperature change, and after a period of poor conditions has been corrected.

Where it becomes a problem is when shed is retained rather than released. A ring of old skin left around a limb, a toe or the tail can tighten as the animal grows and restrict blood flow. The area below it swells and darkens. This is a genuine emergency and it must not be pulled off, because the skin underneath is often not ready and pulling causes injury and infection.

Retained shed usually indicates something else: poor nutrition, water that is too cool, inadequate basking, dehydration in a semi-terrestrial species, or vitamin A deficiency.

Fungal and bacterial skin infection

Water moulds.

Organisms of the Saprolegnia group and their relatives are present in most aquatic environments. They are opportunists rather than aggressive pathogens: they colonise skin that has already been damaged, and they thrive where water is cool, organically loaded and where the animal is never fully dry.

The appearance is characteristic. White to grey, opaque, cotton-like or woolly tufts that adhere to the skin, most often on the neck, the limbs and around the tail. Under water they look fluffy. Out of water they collapse into a whitish film. The skin beneath is usually reddened or eroded.

The three underlying conditions that allow it are nearly always present together: a turtle that cannot dry out, water with a heavy organic load, and a temperature at the low end of what the species needs.

Bacterial dermatitis.

Produces reddened, moist, sometimes ulcerated patches, often with a smell, and it can spread. It arises in the same conditions and frequently alongside fungal disease.

Systemic bacterial disease.

The serious end of the spectrum. Pink or red blotching on the plastron and limbs, pinpoint haemorrhages, ulcers, lethargy, refusal to eat, sometimes limb paresis. It requires veterinary treatment urgently.

Aural abscesses.

A firm swelling on one or both sides of the head behind the eye, in the ear region. In turtles these are solid rather than liquid, are strongly associated with vitamin A deficiency and poor water quality, and require surgery. They are not treatable at home.

Weigh the turtle and write it down. Skin disease that is going the wrong way is nearly always accompanied by a falling weight and a falling appetite.

Water quality as a direct cause

Turtles are heavy waste producers, and a tank stocked and filtered as though it held fish of the same size will not cope.

Ammonia and nitrite are direct irritants. They damage skin and the surface of the eye, and a turtle that repeatedly rubs its eyes with its forelimbs is frequently reacting to a chemical irritation rather than to an infection.

Organic load feeds bacteria and moulds. Uneaten food, particularly protein-rich food, decomposes quickly in a warm tank.

Temperature matters in both directions. Water that is too cool suppresses immune function and slows healing, and it is one of the conditions water moulds prefer.

pH extremes irritate skin and eyes.

The practical measures are unglamorous. Filtration rated well above the actual water volume, regular partial water changes with dechlorinated water, physical removal of waste, and feeding in a separate container so uneaten food never enters the main system. Feeding outside the tank is one of the most effective single changes an owner can make.

Basking: the treatment that is also the prevention

An aquatic turtle needs to leave the water and become completely dry, right down to the skin, every day.

Drying kills water moulds and many bacteria on the skin surface, because they cannot survive desiccation. Ultraviolet light adds to that effect and drives vitamin D3 production, which supports the immune system and the shell. Warmth raises body temperature into the range where the immune system works properly.

A basking area therefore has to do three things: be genuinely out of the water, be warm enough that the turtle stays there long enough to dry, and be under both a heat source and a suitable ultraviolet source.

The common failures are a dock that is partly submerged so the turtle never dries, a lamp too far away or too weak to reach an appropriate temperature, an ultraviolet bulb long past its useful output, glass or plastic between the bulb and the turtle blocking ultraviolet, and a basking site so small or so exposed that a nervous turtle will not use it.

If a turtle never basks, find out why before adding anything to the water. Competition with a tank mate, a lamp that is too bright or too close, a dock that is unstable, or a turtle that is unwell are all common reasons.

Behaviour that gets mistaken for itching

Rubbing the eyes with the forelimbs. Usually irritation from water quality, or vitamin A deficiency, or an eye infection. Test the water and look at the diet.

Rubbing the neck and legs against decor. Common during shedding and generally normal, but persistent rubbing in one area is worth examining.

Scratching at the shell with a hind limb. Usually shedding scutes, algae, or an irritant on the shell.

Fluttering the front claws at another turtle. In several common species, including red-eared sliders, males have elongated front claws and vibrate them at a female's face as courtship. It is not itching. It can, however, be relentless harassment, which stresses the recipient and causes bite injuries, so it is worth watching.

Biting at its own limbs. Uncommon and abnormal. Look for retained shed constricting a limb, an injury or a foreign object.

Clear open eyes and smooth, evenly coloured skin are the baseline. Puffy eyelids and thickened skin point at vitamin A status before they point at infection.

Diet and the skin

Vitamin A deficiency is one of the commonest underlying causes of skin and eye disease in pet turtles, and it comes directly from diet.

It occurs in turtles fed only on a single commercial pellet of poor quality, on an all-meat or all-insect diet, or on pale lettuces that contain very little of anything.

The signs are swollen eyelids, eyes held closed, thickened and poorly shedding skin, aural abscesses, and increased susceptibility to infection everywhere.

The correction is dietary and it should be made with veterinary input, because vitamin A can also be overdosed by injection or supplement, producing skin sloughing of its own. Do not self-treat with a supplement.

Species differ. Some common pet turtles become more herbivorous as adults while juveniles are more carnivorous, and feeding an adult like a juvenile causes both obesity and shell problems. Establish what your species eats at its current age before changing anything.

What never to do

Do not use flea, tick or mite products of any kind on a turtle.

Do not use human antifungal creams, athlete's foot preparations or antibacterial ointments.

Do not use tea tree oil, essential oils, or any aromatic product.

Do not pull, peel or scrub off skin that has not released on its own.

Do not scrub a turtle with a brush unless a vet has specifically shown you how and why.

Do not put a turtle into a salt bath or a chemical dip on internet advice. Concentration, duration and species tolerance all matter, and turtles absorb through the skin and cloaca.

Do not dry-dock a turtle without veterinary instruction. Keeping an aquatic turtle out of water is a real treatment, but done wrongly it dehydrates the animal and stops it eating.

Do not add medications to the tank water.

Do not raise the water temperature dramatically to fight an infection without advice, since it also accelerates bacterial growth in the water.

Do not ignore a red plastron.

The routine that prevents most of this

Check the turtle out of the water once a week, in good light. Look at the neck, all four limbs, the tail, the underside and the head, and compare the two sides.

Weigh weekly on a kitchen scale and record it.

Test the water regularly for ammonia, nitrite, nitrate and pH, and know your normal values.

Feed in a separate container so that waste food never enters the main tank.

Change water partially and regularly, and clean the filter without destroying the biological media.

Confirm the basking site is genuinely dry, warm enough and used. Watch the turtle bask.

Replace the ultraviolet bulb on schedule and record the date, since output falls long before the bulb stops emitting visible light.

Quarantine any new turtle away from the existing animals, with separate equipment, before introduction.

Watch for aggression and basking competition in shared tanks, because bite wounds are the entry point for most skin infections in a group.

When to get help

Go the same day for red or pink blotching on the plastron with a lethargic turtle, for open ulcers, for a swelling behind the eye, for swollen eyelids with appetite loss, and for a constricting band of retained skin on a limb or tail.

Book within days for white adherent patches with red skin underneath, for persistent eye rubbing, for bite injuries from a tank mate, for a turtle that has stopped basking, and for weight loss.

Book a routine appointment for a turtle whose diet has been narrow, whose ultraviolet bulb is of unknown age, or that has never had a health check.

Healthy skin, clear eyes and a turtle that hauls out and dries off every day are what the whole routine is protecting.

Bring dated photographs taken out of the water, current water test results for ammonia, nitrite, nitrate, pH and temperature, the basking surface temperature, the ultraviolet bulb model and installation date, the full diet, the weight record, and details of any tank mates. Expect a reptile vet to want to sample the lesion for cytology and possibly culture, and to spend as much time on the husbandry as on the skin itself, because the skin problem is usually the visible end of an environmental one.