Severe phytophotodermatitis from fig sap: a little known phenomenon

Abstract

A 46-year-old arborist with no medical history presented to the emergency department with a confluent blistering, erythematous, non-pruritic, painful rash covering both arms circumferentially and the back of his neck. He sought medical advice as his arms were becoming more painful and swollen with blister formation, despite aloe vera cream and wet towel wraps. He recalled that 2 days previously he had been pruning a fig tree on a hot sunny day. He was wearing a t-shirt and his forearms had been exposed to a large quantity of fig sap, while he was working under direct sunlight. On examination, there were several blisters with no superimposed infection. He was diagnosed with phytophotodermatitis and referred to a regional burns unit. He recovered well with simple dressings and a course of antibiotics. At present, he has made a good recovery with no long-term sequelae such as skin hyperpigmentation or hypopigmentation.

Background

Fig trees (Ficus caria) are popular in gardens across the UK and worldwide, the fruit of which is widely enjoyed. However, skin exposure to the sap of these trees can lead to a severe sunburn-like reaction, known as phytophotodermatitis, when skin is exposed first to the sap and then to ultraviolet (UV) light. While previously reported in the literature, it still does not appear to be a well-known phenomenon among emergency department (ED) staff or the general public.

It is the authors belief that it is necessary to educate both medical professionals and the general public, particularly those in professions dealing with plants regularly, of the risks associated, in order to prevent exposure and to ensure prompt and appropriate treatment.

Case presentation

A 46-year-old tree-surgeon presented to the ED 2 days after sustaining ‘sunburn’ to both forearms and back of the neck after pruning a common fig tree on a hot sunny day. At the time, he had been wearing a t-shirt and gloves and reported that he continued to work in the direct sunlight despite his arms being covered in sap from the tree. On presentation, he had a painful, non-pruritic erythematous rash circumferentially across both forearms, sparing the hands, which developed a few hours after exposure to the sap and was increasing in severity over time (see figure 1). During the initial 24 hours, he had applied aloe vera cream to the affected areas, believing it to be a simple sunburn. In the following 24 hours, however, his arms became progressively more painful and swollen, with blisters forming and discharging clear serous fluid. He sought medical help as he was no longer able to control the pain with simple measures (aloe vera gel, wet tea towels and paracetamol).

Figure 1.

Images of the patient’s arms at presentation to the emergency department.

At the time, the patient was unaware of the reaction between fig sap and sunlight. However, after speaking with his supervisor who was aware of the phenomenon, he decided to attend the ED.

On examination, he was haemodynamically stable with all observations in the normal range. Both forearms were moderately swollen with diffuse circumferential patchy erythema covering approximately 8% of total body surface area (see images). There were multiple areas of blistering, some of which had spontaneously burst and were oozing serous exudate. The hands were neurovascularly intact bilaterally with strong pulses at the wrist. The back of the neck was also erythematous, but with no blistering. He was apyrexial and there were no clinical features of infection in any of the areas involved. He was otherwise well with no significant medical history, no allergies and no history of rashes.

Investigations

Clinical images were discussed with the regional burns unit.

No further investigations were deemed necessary.

Differential diagnosis

There is a broad differential diagnosis for phytophotodermatitis (box 1). A detailed history and examination are essential. In this case, the patient presented informing the ED team that this was a sunburn injury. However, the distribution of the ‘burns’ and the clinical features did not fit with a simple sunburn. Appearances were more severe than a typical sunburn and some sun-exposed areas, for example, the face were completely spared. The clinical presentation was more typical of contact dermatitis or chemical burns. The patient led the emergency team to the possibility that the fig sap was causative. No member of the ED team on duty, up to consultant level, was aware of this skin reaction (although the team were aware of other similar causative plants such as giant hogweed). An internet search conducted in the department confirmed that the clinical presentation fitted a phytophotodermatitis picture.

Box 1. Differential diagnosis of phytophotodermatitis.

Polymorphic light eruption.

Burns.

Drug photosensitivity¹⁷:

• Antibiotics (doxycycline).

• Antifungals.

• Amiodarone.

• Isotretinoin.

• Sulphonylureas.

• Non-steroidal anti-inflammatory drugs.

• Phenothiazines.

Herpes simplex.¹⁸

Lyme disease.¹⁹

Contact dermatitis.

Collagen vascular diseases (systemic lupus erythematosus, ankylosing spondylitis, dermatomyositis, scleroderma, rheumatoid arthritis, psoriatic arthritis and polyarteritis nodosa).¹⁷

Superficial lymphangitis.²⁰

Non-accidental injury.¹⁸

Treatment

In the ED, the affected areas were cleaned and the blisters were deroofed following administration of analgesia. The skin loss appeared to be superficial (epidermal) in nature with no areas of circumferential skin loss. All areas remained blanching to pressure and sensate.

Following discussion with the regional burns unit, the wounds were dressed with silicone based dressings, and a gauze-bandage overlay. He was given an appointment to be seen by the burns service the following day. The burns team taking the referral were also not familiar with this as a cause of burns.

On presentation to the burns unit, he was febrile and tachycardic, and was, therefore, admitted for observation and commenced on intravenous co-amoxiclav. After 24 hours, he was clinically much improved and was discharged home to complete a 7-day course of oral co-amoxiclav. His arms were dressed with simple dressings (Telfa, Acticoat, gauze and crepe bandage) and he was followed up regularly in the burns dressings clinic until all the wounds were healed.

Outcome and follow-up

Two weeks after presentation to ED, the patient reported that his skin had almost healed completely and he had returned to work. He was advised to use emollient (Diprobase) on the wounds to improve long-term scarring.

At present, the patient has no change in skin pigmentation; however, he has been advised that he is at risk of developing these changes in the future.

Discussion

Phytophotodermatitis is a cutaneous inflammatory reaction caused by the interaction of light sensitising botanical substances called furocoumarins, with ultraviolet light (specifically long wave UVA).^1–3 The UV activated furocoumarins damage cells by binding to nuclear DNA and RNA and cause disruption of the cell membrane, resulting in oedema and cell necrosis.⁴ The specific reaction from fig sap is caused by the furocoumarin 8-methoxypsoralen.⁵ Widespread burning erythema, blistering and bullae often develop within 24 hours of exposure and may peak in severity up to 72 hours. Interestingly, it has been noted before that wet skin and sweat worsens the cutaneous reaction, as we have seen in this case.⁶ Some of the most severe cases documented in the literature occur from fig sap, with severe burns covering 81% total body surface being reported after exposure to fig furocoumarin.⁷

A wide range of common garden plants have been implicated, including parsley, parsnips, celery, carrot, lime, lemon, bergamot oranges and several wild flowers (umbelliferae), hogweed⁸ and fig in this case.^9–11 At present, no studies have directly compared the severity of the condition with exposure to different sources of furocoumarin.

A few cases have been reported in the medical literature and treatment depends on the severity of the reaction. Severe cases affecting a large total body surface area should be managed in burns units (in the acute phase) and by dermatologists (usually for late manifestations of hyperpigmentation or hypopigmentation). The majority of reported cases affect an area <1% and are usually related to drips of juice or sap.¹² We believe this to be one of the most widespread and severe cases documented in the literature. The confluent area affected is likely a result of the patient rubbing his arms during the course of his work and as a result spreading the sap over a wider area.

Phytophotodermatitis is generally self-limiting and symptomatic management with analgesia is the mainstay of treatment; however, more severe cases may require more specialised treatment. Topical steroids may be of use when treating moderately severe cases, while oral steroids have been used in severe widespread lesions.¹³ Antibiotics are indicated if bacterial superinfection is suspected.¹³ At present, no guidance exists regarding management of this condition and we believe it is frequently misdiagnosed. Possible misdiagnoses include chemical burns, atopic dermatitis, hypersensitivity reactions, drug reactions, allergic contact dermatitis, cellulitis, fungal infection, bullous impetigo, herpetic lesions and even non-accidental injury in children.^{14 15}

If misdiagnosed, patients could receive incorrect treatment with potentially harmful side effects due to lack of knowledge of the condition. The management for this condition differs from other types of burn or skin reaction as steroids may also be used as a mainstay of treatment—topical if moderately severe, oral if widespread. In addition, antibiotics are indicated if there are any signs of infection, as they were in this case.

Correct diagnosis of the condition is essential for appropriate management and counselling of patients regarding the possibility of long-term changes in skin pigmentation, that are not seen in simple sunburn. In most cases, hyperpigmentation develops in 1–2 weeks following exposure and may persist for a number of months. However, in some cases, reactions from fig tree sap instead causes hypopigmentation, thought to be due to melanocyte apoptosis.¹⁶ Prompt referral to dermatology may be indicated for consideration of treatments such as bleaching creams for hyperpigmentation, which may reduce the long-term effects.

Correct diagnosis of the causative plant is also essential to prevent further episodes of the same exposure. Once the causative plant has been identified and the phenomenon explained to patients by the diagnosing clinician, these individuals are able to avoid future contact with sap by avoiding the plant or taking preventative measures, and will ensure they present to medical services early following any subsequent exposures as early management may prevent long-term sequelae. Individuals may also wish to put up warning signs around such plants, particularly in public areas, as is the case for giant hogweed. If identified correctly, risk-reducing advice can be given to wear adequate personal protective equipment and further cases can be prevented.

Despite the common nature of the plants involved, there is very little awareness of the condition among the general population. The most well-known plant implicated is the giant hogweed (Heracleum mantegazzianum), which is often accompanied by public health notices when found in public parks.⁸ However, individuals are much more likely to contact many of the other plants in their day-to-day lives both through gardening and food preparation.

In summary, phytophotodermatitis results from skin contact with furocoumarins, followed by UV light exposure. It is essential that physicians consider this as a possible diagnosis in patients presenting with apparent sunburn, particularly where this has continued to develop for 24–48 hours after exposure. Patients should then be referred to the local burns or dermatology service. Individuals working in high-risk occupations, such as tree surgeons, should also be educated and encouraged to wear protective clothing when working with hazardous plants, particularly in sunny weather.

Patient’s perspective.

I wish I had known about the risks of this plant, as I would have changed my clothing to handle it in the hot weather. I work with trees all the time but had not heard of this, although my boss did know about it and advised me to attend the hospital. I think it is important that the public and doctors know about this so they can protect themselves and help other patients like me.

Learning points.

• Consider phytophotodermatitis in presentations of severe, blistering sunburn, particularly when the onset of severe symptoms is delayed from the exposure.

• Emergency departments should be educated on the range of plants that can result in such a reaction.

• Consider plant exposure in all patients attending with unusual skin presentations, particularly in those with relevant occupations.

• Consider referral to dermatology as there is the potential for long-term sequelae—notably skin hyperpigmentation—in these patients.