Published by Ys Pharma Inc., the company that makes KADASON Medicated Shampoo, which is mentioned in this article. This article has not been medically reviewed. Label details checked October 29, 2026.
Before you start: check the label
Medicated shampoos don't all use the same directions. Before your first wash, read the Directions and Warnings on your product's Drug Facts label. They tell you how to apply it, whether to leave it on before rinsing, and how often to use it. If a dermatologist has given you a routine, follow that.
How to use medicated shampoo in 4 steps
4 Key Steps at a Glance
| Step | How to do it |
|---|---|
| 01Wet hair & scalp | Wet your hair and scalp thoroughly. Lukewarm water works well for most people. |
| 02Apply to scalp | If your hair is thick or long, part it and apply the shampoo in sections so it reaches the skin. Focus on your scalp, where flakes and scale form, rather than the lengths of your hair. |
| 03Lather gently | Gently work the shampoo into a lather using the pads of your fingers. Avoid scratching with your nails. |
| 04Rinse thoroughly | Follow your product's directions on how long to leave it on, then rinse until no lather is left on your scalp. KADASON's label does not specify an additional waiting period: work into a lather and rinse thoroughly. More on contact time below. |
After rinsing: conditioner isn't a required step. If your hair feels dry after washing, you can apply conditioner mainly to the lengths and ends; if you're unsure which products to use on your scalp, ask your dermatologist. Pat your hair dry gently with a towel rather than rubbing hard.
How long should you leave medicated shampoo on your scalp?
It depends on the product. There is no single contact time that applies to every medicated shampoo.
- Follow the label. Some products tell you to leave the lather on for a set time before rinsing. Others, like KADASON, don't specify a waiting period: the directions are to work into a lather and rinse thoroughly.[1]
- Follow your dermatologist, if you have one. The American Academy of Dermatology (AAD) advises leaving the shampoo on your scalp for the amount of time your dermatologist recommends.[3]
- Longer isn't automatically better. Don't leave a shampoo on longer than its label or your doctor directs in the hope that it will work better.
How often should you use it?
- KADASON: the label says: "for best results, use at least twice a week or as directed by a doctor."[1] This is the direction for KADASON specifically.
- Medicated shampoos in general: how often you use one depends on the active ingredient, the product's label, the state of your scalp and your hair type. Other products may have different directions, so read the label of the one you use.[2]
- By hair type: the AAD notes that people with straight or wavy hair may use dandruff shampoo 2 to 3 times a week, while a dermatologist may recommend once a week for curly or tightly coiled hair.[3] This is general guidance, not a direction for any one product.
For more on building a routine around a medicated shampoo, read Top 10 Shampoos for Managing Seborrheic Dermatitis.
Common medicated shampoo mistakes
| Mistake | Why it matters | Do this instead |
|---|---|---|
| Ignoring the product's contact-time directions | Some products need time on the scalp before rinsing; others don't specify a wait | Read the Directions and follow them as written |
| Washing only the hair | Flakes and scale form on the scalp | Part your hair and apply the shampoo to the skin |
| Scratching with nails | Can break the skin and add to irritation | Use the pads of your fingers |
| Keeping a product that leaves your scalp irritated or coated | Irritation or residue makes it harder to tell how your routine is working | If an oil or styling product irritates your scalp or leaves it feeling coated, keep it off the scalp or pause it |
| Switching products every few days on your own | You can't tell what is working | Use one product as directed before judging it. If your dermatologist has you alternate two medicated shampoos, follow that plan.[3][4] |
When should you expect results?
There is no single timeline. Products differ in their directions and in when their labels say to check in with a doctor, so judge a shampoo by its own label.
- Use the shampoo regularly, as its label directs, before you decide whether it is working.
- If your symptoms get worse, stop using it and ask a doctor.
- If there is no improvement after regular use as directed, talk to a healthcare professional rather than adding more products.
- Once your symptoms settle, follow the label or your doctor's advice on how often to keep using it.
When to stop and ask a doctor
General precautions for medicated dandruff and seborrheic dermatitis shampoos
The FDA's rules for these over-the-counter shampoos require labels to include warnings such as:[2]
- For external use only.
- Avoid contact with the eyes. If contact occurs, rinse eyes thoroughly with water.
- Stop use and ask a doctor if your condition worsens or does not improve after regular use as directed.
- For seborrheic dermatitis: if the condition covers a large area of the body, consult your doctor before using the product.
Children: check the label for age directions, and ask a doctor before using a medicated shampoo on a child. For babies with cradle cap, the AAD says dandruff shampoo is not recommended.[3]
KADASON's label warnings
These come from KADASON's own Drug Facts label. Other products have their own warnings.[1]
- For external use only.
- Do not use for prolonged periods without consulting a doctor.
- Avoid contact with the eyes. If contact occurs, rinse eyes thoroughly with water.
- Stop use and ask a doctor if your condition worsens or does not improve after regular use as directed.
- If pregnant or breastfeeding, ask a health professional before use.
- Keep out of reach of children. If swallowed, get medical help or contact a Poison Control Center right away.
How to use KADASON Medicated Shampoo
If you are using KADASON, here is what its Drug Facts label says:[1]
- Active ingredient: salicylic acid 1.8%
- Use: for relief of the symptoms of seborrheic dermatitis
- Directions: wet hair; apply shampoo and work into a lather; rinse thoroughly; for best results, use at least twice a week or as directed by a doctor
- Key warning: do not use for prolonged periods without consulting a doctor
- Size: 8 fl oz (237 mL)
KADASON is sold under the FDA's over-the-counter monograph for dandruff, seborrheic dermatitis and psoriasis products. Products sold this way are not individually approved by the FDA.[2]
Explore KADASON Medicated Shampoo →
Related reading
- Scalp Psoriasis vs. Seborrheic Dermatitis: How to Tell the Difference
- Salicylic Acid vs. Ketoconazole Shampoo: Which Is Better?
- Best Shampoo for Seborrheic Dermatitis: 4 Options Compared
- The Complete Guide to Choosing the Best Seborrheic Dermatitis Shampoo
References
- DailyMed. KADASON Medicated (salicylic acid) shampoo, Drug Facts, NDC 87263-927
- U.S. FDA. 21 CFR 358.750 – Labeling of drug products for the control of dandruff, seborrheic dermatitis, or psoriasis (eCFR)
- American Academy of Dermatology. Seborrheic dermatitis: Diagnosis and treatment
- Mayo Clinic. Seborrheic dermatitis – Diagnosis and treatment
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