| In clinical studies, the most frequently observed side effects included application site burning, application site pruritus and application site erythema.Frequencies of side-effects observed in clinical studies and given in the table below are defined according to the MedDRA frequency convention:Very common ( 1/10), Common ( 1/100, <1/10), Uncommon ( 1/1,000, <1/100), Rare ( 1/10,000, <1/1,000), Very rare (<1/10,000), Not known (cannot be estimated from the available data). | System Organ Class | Very Common | Common | Uncommon | Rare | | Skin and subcutaneous tissue disorders | | | seborrhoea, acne, skin depigmentation
| cheilitis
| | General disorders and administration site conditions | application site burning, application site pruritus, application site erythema
| application site exfoliation, application site pain, application site dryness, application site discolouration, application site irritation
| application site paraesthesia, application site dermatitis, application site discomfort, application site oedema
| application site vesicles, application site eczema, application site warmth, application site ulcer
| | Immune system disorders | | | | drug hypersensitivity
| Generally, local skin irritation regresses in the course of treatment. Rash has been reported rarely in post-marketing surveillance.Worsening of asthma in patients treated with azelaic acid has been reported rarely during post-marketing surveillance (the frequency is not known).
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