Applying Ointments and Creams Correctly: Fingertip Units, Order & Cortisone Rules

With tablets, the dose is printed on the pack. With ointments and creams you decide it yourself — every single time you apply them. And the most common dosing error is not too much, but too little. This guide explains the fingertip unit, the difference between an ointment, a cream, a gel and a lotion, the order of active ingredient and emollient — and why “apply thinly” means something different with cortisone than most people think.

1. Why the amount decides whether it works

A topical medicine — a medicine applied to the skin — consists of an active ingredient and a base. The base helps determine how much of the active ingredient gets through the stratum corneum, the outer horny layer. The dose follows from the amount, the area, the frequency and the duration — and only the last of those is usually stated clearly in the package leaflet.

Two opposite mistakes follow from this. One: a finger-thick layer that does not sink in and still does not work any better. The other, far more common: an amount so sparing that the area is not fully covered. The flare then does not settle, treatment drags on for weeks — and in the end more active ingredient has been used up than in a short, adequately dosed course.

2. The fingertip unit: a measure everyone has to hand

The fingertip unit (FTU) turns “apply thinly” into something you can actually check. It is described as a practical measure in the guideline on atopic dermatitis, among others.^¹

This is how you measure it: from a tube with a standard nozzle (about 5 millimetres) you squeeze a line of cream onto your index finger — from the tip to the first crease. In adults that is around 0.5 grams and is enough for about two flat palms, roughly two per cent of the body surface.

These figures are guide values for adults of average build. Much smaller amounts apply to children, because body surface and hand size do not grow in proportion; the child-appropriate figures come from the paediatric practice.

3. Ointment, cream, gel or lotion: the fat-and-water principle

The same active ingredient can sit in different bases — and then works to a different degree. The difference lies in the ratio of fat to water.^²

• Ointment: rich in fat, low in water. Lies on the skin like a film and increases absorption. Ideal for dry, scaly skin — unsuitable on weeping areas.
• Cream: a mixture of fat and water. The all-rounder for everyday use: sinks in faster than an ointment, is greasier than a lotion.
• Lotion: high in water and thin, for large areas and hairy regions. Cools, but leaves little fat behind.
• Gel: fat-free, cooling, sinks in without residue. Good for oily regions; on cracked skin it can sting.

From this comes the dermatological rule of thumb: wet on wet, fat on dry. A weeping area tolerates watery preparations; dry, cracked skin needs fat. The other way round, both get worse — a greasy ointment traps moisture on weeping eczema, and a lotion dries psoriasis out further.

That is why rich, fatty bases are often used for psoriasis, while light gels are used for acne and rosacea; with atopic dermatitis the base changes with the season. With athlete's foot, a cream suits the spaces between the toes better, while an ointment with the same active ingredient suits the dry sole — clotrimazole, for example.

4. Step by step: how to apply it properly

1. Wash your hands — so that no germs get into the tube or onto the skin.
2. Prepare the skin: cleanse with lukewarm water, no harsh soaps, pat dry gently instead of rubbing.
3. Measure the amount: deliberately squeeze out the number of fingertip units from the table, rather than going by feel.
4. Spread it in portions: place several small dabs first and only then spread them out — that way it goes on evenly.
5. Spread in the direction of hair growth, gently and over the whole area. Rubbing it in vigorously only causes extra irritation.
6. Let it sink in: two to five minutes before clothing or a second preparation goes on top.
7. Wash your hands — unless your hands are themselves the area being treated.
8. Close the tube and label it: note the opening date with a waterproof pen.

With jars there is one more rule: do not reach in with your finger, use a clean spatula instead — otherwise germs end up in a pot that stands open for weeks.

5. Cortisone creams: “thinly” does not mean “homeopathically”

No other topical medicine is dosed wrongly as often as a cortisone-containing cream — and the reason is rarely carelessness, it is caution: out of respect for cortisone, many people deliberately apply less than they were prescribed. Specialists call this steroid phobia.^²

The problem: with topical cortisone, under-treatment is a more common mistake than over-treatment. If too little is applied, the flare does not settle and the treatment is extended again and again — and that is exactly how the long duration of use that should be avoided comes about. A short, adequately dosed course is as a rule gentler on the skin than weeks of half-hearted treatment.

In concrete terms, “apply thinly” means an even, continuous film that covers the area completely and sinks in after a brief spread — nothing should be left sitting on top, but no gap should be left open either. The fingertip unit translates precisely that into an amount.

Potency classes I to IV: what the classification is for

Topical glucocorticoids are usually divided into four potency classes. The classification serves as a guide — which class is used where is decided by the treating practice.^³

• Class I (mild): hydrocortisone — the face, children, sensitive areas, short-term.
• Class II (moderate): prednicarbate, hydrocortisone butyrate, triamcinolone acetonide — eczema on the trunk and limbs.
• Class III (potent): mometasone furoate, methylprednisolone aceponate, betamethasone valerate — acute flares, thicker areas of skin.
• Class IV (very potent): clobetasol propionate — palms, soles, stubborn patches, short-term.

One representative of class III is mometasone, which in many preparations is applied only once a day. That is not about economising: for most modern steroids, according to the product information, a second application on the same day brings no additional benefit, because the stratum corneum acts as a reservoir. Cortisone in tablet form, such as prednisolone, is a different matter — other rules apply there, particularly when stopping. The basics of both are covered in the cortisone guide.

6. Areas to treat with care: face, skin folds, genitals

Skin is not the same everywhere: in some places the stratum corneum is thin, in others skin lies on skin and acts like a natural occlusive dressing. Both increase absorption considerably:

• The face, and the eyelids in particular — the thinnest skin on the body
• Neck, armpits, groin, the fold under the buttocks and under the breasts — skin on skin, warm and moist
• The genital and anal region
• The entire body in babies and toddlers

Weaker potency classes and shorter periods are generally chosen there. Possible unwanted effects of use that is too long or too potent: thinning of the skin (atrophy), enlarged small blood vessels, stretch marks and, on the face, perioral dermatitis — a rash around the mouth and nose that improves under cortisone at first and then gets worse. Rosacea can also deteriorate. Separate rules apply to children; there is an overview in Medications for children.

7. Intermittent treatment and tapering: how to come back off it

Starting cortisone is easy. Stopping it is the part where many courses of treatment fail — usually because the cream is dropped from one day to the next and the complaints promptly return. That is then read as “becoming dependent on the cream”, but it is usually a sign that the underlying condition was still active.

Proactive treatment in atopic dermatitis

For atopic dermatitis there is an established two-stage approach that the guideline describes.^¹ During an acute flare, treatment is daily until the patches have healed. What follows is not an abrupt end but proactive treatment: the active ingredient continues to be applied on one or two fixed days a week to the areas previously affected — even when nothing can be seen there. Daily emollient care carries on alongside it.

The thinking behind it: the skin looks healed but stays subtly inflamed for weeks. Intermittent use catches that phase and can reduce the number of new flares without increasing the amount of active ingredient used. Whether the schedule suits you is decided by the treating practice.

Tapering after longer use

If treatment has run for longer than a few weeks, or with a potent class, tapering step by step makes sense. Two approaches are usual and can be combined: first reduce the frequency (daily → every other day → twice a week), then the potency (class III → II → I). In psoriasis, topical cortisone is often combined with vitamin D3 analogues and used in intervals.^⁴

One point calls for honesty: after a short course over a few days, no tapering is needed. You will find the full account in Stopping cortisone.

8. The order: emollient first or active ingredient first?

This question comes up again every morning as soon as two products are involved. The evidence is thin: there is no solid body of studies showing one order to be superior — only pharmaceutical plausibility and a broad consensus in practice:

• The active ingredient onto clean, dry skin — a layer of emollient underneath dilutes it and spreads it over healthy areas.
• Leave a gap when both are used on the same day — as a rule of thumb 15 to 30 minutes, so that the first layer has sunk in.
• Simpler still: separate them in time — active ingredient in the evening, emollient care in the morning and after showering. That sidesteps the question entirely.
• Do not mix them in your hand — that changes the concentrations. Apply them one after the other, not together.
• Different active ingredients on different areas — and where that is not possible, with a clear gap in time.

One point matters more than the order itself: in atopic dermatitis, emollient care is not an optional extra. Daily care over the whole body lowers the number of flares — and it is the first thing to be dropped as soon as the skin is calm. But that is exactly when the next flare begins. Tying the care to a fixed everyday routine (after showering, before going to bed) makes it easier to keep up.

9. After applying: hands and sun

Wash your hands — even when there is nothing to see

After applying, active ingredient stays on your fingers and gets to places where it does not belong: into the eye, onto the lips, onto other people's skin. This is called self-contamination and, where other people are affected, unintentional transfer — a well-known point in the product information for hormone-containing gels. The same principle applies to tablets: pregnant women should not handle broken finasteride tablets, because the active ingredient is absorbed through the skin. For creams that means: wash your hands before you pick up your child or put in contact lenses.

Sun: not every active ingredient tolerates UV light

Some applied active ingredients increase sensitivity to light — the skin then reacts after only a short time with sunburn-like redness. This is known for certain acne treatments and for retinoids, which are also used systemically as isotretinoin.^⁵ In practice: apply the active ingredient in the evening and use sun protection during the day — and put that on last, once the active ingredient has sunk in. Rich ointments also leave stains, and airtight coverings increase absorption: cling film or an occlusive dressing only on instruction. More on this in Medications and sun.

10. Shelf life after opening and correct storage

The printed expiry date applies to the unopened pack. From the moment you open it, a second, shorter period starts — the in-use shelf life after opening. It is given in the package leaflet and varies considerably:

• Industrially manufactured creams in tubes: often several months after opening — the specific figure is in the package leaflet.
• Pharmacy-compounded preparations: considerably shorter — the date on the label is binding.
• Preparations without preservatives: the shortest of all, often only a few weeks.
• Eye ointments: particularly tightly limited once opened.

From this follows the single most important step: write the opening date on the tube. Without a note there is no way to work out later whether the cream has been open for three weeks or three years — and in case of doubt it gets used anyway.

On storage: creams like neither heat nor frost, and the bathroom is a poor place because of the damp and the swings in temperature. Emulsions separate in the heat — if a cream looks oily or grainy, smells different or has changed colour, it belongs in the bin, even if the date is still fine. More on this in Storing medications correctly and Medications and heat.

11. The most common mistakes at a glance

12. How brite helps you with your skin treatment

Keep your skin treatment under control — with brite

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