Systemic type 2 inflammation encompassing T helper 2 (T_H2)-type responses is emerging as a unifying feature of both classically defined allergic diseases, such as asthma, and a range of other inflammatory diseases. Rather than reducing inflammation with broad-acting immunosuppressants or narrowly targeting downstream products of the T_H2 pathway, such as immunoglobulin E (IgE), efforts to target the key proximal type 2 cytokines — interleukin-4 (IL-4), IL-5 and IL-13 — represent a promising strategy to achieve therapeutic benefit across multiple diseases. After several initial disappointing clinical results with therapies targeting IL-4, IL-5 or IL-13 in asthma, applying a personalized approach achieved therapeutic benefit in an asthma subtype exhibiting an 'allergic' phenotype. More recently, efficacy was extended into a broad population of people with asthma. This argues that the Type 2 inflammation is broadly relevant across the severe asthma population if the key upstream drivers are properly blocked. Moreover, the simultaneous inhibition of IL-4 and IL-13 has shown significant clinical activity in diseases that are often co-morbid with asthma — atopic dermatitis and chronic sinusitis with nasal polyps — supporting the hypothesis that targeting a central 'driver pathway' could benefit multiple allergic diseases.