Natroba Side Effects: What to Expect and When to Call Your Doctor

If you've been prescribed Natroba (spinosad topical suspension 0.9%) for head lice or scabies, you probably want to know what side effects to expect. The good news: Natroba has a strong safety profile and is generally very well-tolerated, even in young children. But like all medications, it's important to know what's normal, what to watch for, and when to call your doctor.

Is Natroba Safe?

Yes. Spinosad — the active ingredient in Natroba — is derived from a naturally occurring soil bacterium (Saccharopolyspora spinosa) and is not systemically absorbed following topical application. Studies using double the active amount found in Natroba (spinosad 1.8%) showed no systemic absorption in patients as young as 4 years. There is no evidence of neurotoxicity, developmental toxicity, immunotoxicity, mutagenicity, or carcinogenicity from spinosad exposure.

Common Side Effects: Head Lice Treatment

In clinical trials for head lice treatment, the side effects occurring in more than 1% of patients were:

Application site erythema — Redness or mild irritation at the scalp where the product was applied. This is the most commonly reported side effect.

Ocular erythema — Redness of the eyes. This typically occurs if the product accidentally gets into the eyes during application.

Less common reactions (occurring in less than 1% but more than 0.1% of patients) included application site dryness.

Common Side Effects: Scabies Treatment

For scabies treatment (where the medication is applied to the whole body from neck to toes), the side effects occurring in more than 1% of patients were:

Application site irritation — Including pain and burning at the skin where the product was applied

Dry skin — Generalized skin dryness following treatment

Serious Warnings: Who Should Not Use Natroba

While Natroba is safe for most patients, there are important contraindications and warnings:

Not approved for infants under 6 months: Natroba contains benzyl alcohol, which has been associated with serious adverse reactions and death in neonates and low birth-weight infants when administered IV. Do NOT use Natroba on infants under 6 months.

Allergic reactions: Stop using Natroba and seek emergency care if you develop hives, difficulty breathing, swelling of the face, lips, tongue, or throat.

Eye exposure: If Natroba gets into the eyes, rinse thoroughly with water immediately. If redness or irritation persists, contact your healthcare provider.

For external use only: Do not swallow, inhale, or apply to areas other than directed.

When to Call Your Doctor

Contact your healthcare provider if:

Skin or scalp irritation is severe or does not resolve after a few days

Eye redness or irritation persists after rinsing

You develop an allergic reaction (rash, swelling, difficulty breathing)

You still see live lice 7 days after treatment (a second application may be needed)

Scabies symptoms (intense itching, rash) persist or worsen 2–4 weeks after treatment

Side Effects vs. Normal Post-Treatment Reactions

Important: Itching and irritation from the lice or scabies infestation itself may continue for several days to weeks after successful treatment as your immune system responds to dead parasites. This is normal and does not mean the treatment failed. Use anti-itch creams or oral antihistamines (if recommended by your doctor) to manage residual symptoms while your skin heals.

For information on drug interactions with Natroba, see our guide on Natroba drug interactions. If you're having trouble filling your Natroba prescription, medfinder can help you find pharmacies that have it in stock.