17th January 2024

Management

The mainstay of treatment for HP revolves around reducing/removing exposure to any identified causative allergens. Patients are advised to avoid either an allergen they are known to be sensitive to, or other potential allergens that may be present in their environment. This can be difficult, especially if the allergen is linked to their livelihood. Total avoidance can result in regression of disease and/or prevent progression to fibrosis, so the importance of avoiding causative allergens must be emphasised and encouraged.

Acute and sub-acute HP 

For mild cases of acute HP, steroids are not recommended as the clinical presentation will often improve once the causative allergen is removed. If symptoms are recurrent and persistent, despite allergen avoidance, a short course of oral steroids can be offered if no contraindications are present. These can usually be tapered off unless fibrosis is present – patients in this group normally require long-term low-dose therapy.

Prednisolone is the 1st line oral steroid choice, and dosing is 0.5-1mg/kg/day on average. When symptoms improve, the dose can be tapered by about 5mg every other day over 4-6 weeks, depending on the ongoing clinical presentation.

Chronic HP

For those with chronic HP of a fibrotic nature, smoking avoidance/cessation, seasonal respiratory vaccinations and chest physiotherapy are recommended in addition to the above management strategy. For some, long-term oxygen therapy may eventually also be needed. Use of immunosuppressive agents such as azathioprine and mycophenolate mofetil (MMF) are not currently part of standard care, and further data is needed to support their use in this condition.

For those with very severe disease, lung transplant may be an option, depending on comorbidities, functional status and overall suitability for transplant. There have been several reports of the condition reoccurring in the transplanted organ, likely due to ongoing exposure to the allergen post-procedure.