Antiseptik digunakan untuk membersihkan kulit.

Because digunakan is a passive form.

• menggunakan = to use / uses in an active sentence, where the subject is the doer
• digunakan = is used / are used in a passive sentence, where the subject is the thing being used

So:

• Antiseptik menggunakan... would mean Antiseptic uses..., which does not make sense here.
• Antiseptik digunakan... means Antiseptic is used...

This is very natural in Malay when talking about the function or purpose of something.

The prefix di- usually marks the passive voice in Malay.

So:

• gunakan = use
• digunakan = is used / are used

In this sentence, Antiseptik digunakan... literally means Antiseptic is used...

Do not confuse this di- with the separate word di meaning at / in / on for location.

• digunakan = one word, passive verb
• di rumah = two words, at home

The base word is guna, which means use.

From that root, you can get:

• guna = use / useful use
• menggunakan = to use
• digunakan = is used
• kegunaan = use, function, usefulness
• pengguna = user

So digunakan is built from guna plus affixes.

The ending -kan is part of the verb formation from guna.

In practice, learners usually meet it as part of the standard verb:

• menggunakan = to use
• digunakan = to be used

You do not usually treat di- alone as enough here; the normal passive counterpart of menggunakan is digunakan.

So it is best to learn gunakan / menggunakan / digunakan as a related family.

untuk means for or to, depending on context.

In this sentence:

• digunakan untuk membersihkan kulit
• is used to clean the skin / is used for cleaning the skin

So untuk introduces the purpose of the antiseptic.

Because membersihkan means to clean in the sense of to clean something.

The structure is:

• untuk + verb
• for / to + do something

So:

• untuk membersihkan kulit = to clean the skin

This is a very common pattern in Malay.

bersih is an adjective meaning clean.

• Kulit itu bersih. = The skin is clean.

membersihkan is a verb meaning to clean something.

• Mereka membersihkan kulit. = They clean the skin.

So in your sentence, the meaning needed is an action, not a description. That is why membersihkan is used, not bersih.

The base word is bersih, meaning clean.

With affixes, it becomes:

• bersih = clean
• membersihkan = to clean something
• pembersih = cleanser / cleaning agent
• kebersihan = cleanliness

So membersihkan kulit literally means to make the skin clean.

Malay does not use articles like a, an, and the the way English does.

So:

• kulit can mean skin, the skin, or a skin, depending on context

In this sentence, English naturally translates it as the skin, but Malay simply says kulit.

This is very normal in Malay, and context tells you the intended meaning.

Not always. Kulit has several meanings depending on context, including:

• skin
• peel
• rind
• bark
• outer layer

But in this sentence, because it is about antiseptic and cleaning, kulit clearly means skin.

Yes, depending on context.

Malay nouns often do not show singular/plural unless something makes it clear.

So antiseptik could mean:

• antiseptic
• antiseptics

In many general statements, English may choose singular or plural depending on style:

• Antiseptic is used to clean the skin.
• Antiseptics are used to clean the skin.

Both can be reasonable translations in the right context.

Yes, it is natural and correct.

It is a straightforward formal or neutral sentence explaining the purpose of antiseptic. It sounds like something you might see in:

• a textbook
• health information
• a product description
• educational material

Malay often uses this kind of passive structure for definitions and general facts.

Yes, bagi is possible in some formal styles, but untuk is more common and more straightforward for learners.

So:

• digunakan untuk membersihkan kulit = very common
• digunakan bagi membersihkan kulit = possible, often more formal

If you are learning everyday standard Malay, untuk is the safer choice.

Yes. An active version would need a doer, for example:

• Doktor menggunakan antiseptik untuk membersihkan kulit. = The doctor uses antiseptic to clean the skin.

Your original sentence has no doer because the focus is on antiseptic and its function, not on who uses it.

That is why the passive version is appropriate.

Because Antiseptik itself is already the subject.

The sentence structure is:

• Antiseptik = subject
• digunakan = passive verb
• untuk membersihkan kulit = purpose phrase

Malay does not need an extra pronoun here. English also would not say Antiseptic it is used...

The original sentence is already normal, but in casual speech people might prefer more active or conversational wording, such as:

• Antiseptik dipakai untuk bersihkan kulit.
• Kita guna antiseptik untuk bersihkan kulit.

These are less formal. Your original sentence is better for standard written Malay.

Yes, kulit is the object of membersihkan.

• membersihkan = to clean something
• kulit = skin

So membersihkan kulit means to clean the skin or to clean skin.

Malay does not need a separate object marker here. The verb simply takes its object directly.

Yes. In this sentence, it clearly shows purpose, not future time.

Malay does not mark infinitives the same way English does, so untuk + verb often expresses:

• purpose
• function
• intended use

So here it means:

• for cleaning the skin
• to clean the skin

not will clean the skin.