Post-scabies syndrome: This condition is characterized by persistent itching and skin lesions after successful treatment of scabies, which could be exacerbated or triggered by the use of oral ivermectin. The timing and symptoms align closely with what is expected in post-scabies syndrome.

Allergic reaction to ivermectin: Although rare, an allergic reaction to ivermectin could cause itching among other symptoms. This would be a direct response to the medication rather than the scabies itself.
Persistent scabies infestation: If the treatment with oral ivermectin was not fully effective, or if re-infestation occurred, itching could persist due to the ongoing presence of the scabies mite.
Dry skin (xerosis): Oral ivermectin might indirectly contribute to dry skin, which can cause itching, especially in individuals prone to dry skin conditions.

Hypersensitivity reactions: While rare, severe hypersensitivity reactions (including anaphylaxis) can occur with ivermectin and would be life-threatening if not promptly recognized and treated.
Drug-induced liver injury: Ivermectin is generally safe, but like all medications, it can cause liver injury in rare cases. Severe liver injury could present with itching as part of its symptomatology.

Eosinophilic folliculitis: A condition characterized by an itchy, follicular eruption, which could potentially be triggered by the use of certain medications, including ivermectin, in susceptible individuals.
Mastocytosis: A rare condition where there is an accumulation of mast cells in one or more organs, which can cause itching among a wide range of other symptoms. The use of ivermectin might theoretically exacerbate symptoms in someone with mastocytosis, although this would be highly unusual.