1 Introduction

Multiple chemical sensitivity (MCS) is a chronic condition characterized by recurrent multisystem symptoms triggered by common airborne chemicals, such as fragranced products, new furnishing or smoke from woodburners, at levels below those expected to produce symptoms [1,2,3]. Symptoms from the central nervous system (CNS) such as headache, exhaustion and cognitive deficits are particularly frequent in MCS but symptoms from airways, muscles and joints are also commonly reported [4,5,6]. The pathophysiology of MCS is unexplained, but many theories have been suggested [7,8]; perhaps the most persistent is that of abnormal and amplified processing of sensory signals in the CNS, i.e., neural sensitization. Neural sensitization is defined as an increased central response to a normal sensory input [9,10]. Several recent scientific findings support this hypothesis. Firstly, brain imaging studies have shown reduced brain activation of odour processing regions during odour provocation in MCS patients compared with healthy controls [11,12]. This has been suggested to reflect a reduced cerebral inhibitory activity, thus resulting in neural sensitization [12]. Secondly, controlled experimental pain studies with capsaicin (the active component in chilli peppers) in MCS patients have demonstrated enlarged areas of capsaicin-induced secondary mechanical hyperalgesia [13,14]. Secondary mechanical hyperalgesia reflects an increased mechanical sensitivity in the skin surrounding the capsaicin injection site and is regarded as a CNS response. In accordance with these findings and observations, a single high-level exposure or chronic low-level chemical exposures as well as life stressors have been reported to precede MCS [15] and may trigger plastic CNS changes resulting in an altered response to chemosensory input [9].

MCS can severely impact patients’ lives, often in terms of social and/or occupational disability. Hence, an effective treatment for MCS is urgently needed. However, only few intervention studies on MCS have been published [16,17]. One case study reported a successful treatment outcome using a therapeutic approach combining psychological desensitization and pharmacological treatment with a selective serotonin reuptake inhibitor [18]. Another case study reported a transient but, nevertheless, substantial effect of electroconvulsive therapy (ECT) in cases with MCS [19]. However, ECT is a less attractive treatment as it depends on general anaesthesia and muscle relaxants and may be associated with adverse effects such as transient amnesia. Pulsed electromagnetic fields (PEMF) are a newer technology that utilizes magnetic stimulation to achieve electrical currents in the brain without the disadvantages of ECT. The principle of PEMF is based on alternating magnetic fields, which may activate the underlying neural tissue through activation of intracellular signalling [20]. PEMF has been used for several purposes [21,22,23,24,25,26,27] including neuronal activation [28], enhancing peripheral nerve regeneration [29,30,31,32], and treating depression [33,34] and chronic pain [35,36]. In a previous placebo-controlled study applying PEMF for treatment-resistant depression, the following adverse effects were reported in 1–3 of 25 patients in the active group: increased dream activity, suicidal ideation, tremor, paresthesia, dizziness, constipation, stranguria/voiding problems, increased sweating, helmet felt heavy, flu-like symptoms, lower back pain and stabbing pain in the head [34]. The aims of the present study were to investigate whether PEMF therapy was associated with positive effects on MCS in terms of symptom severity and functional impairments and whether this therapeutic procedure was feasible in MCS patients.

2 Materials and methods

The study was approved by the Danish Data Protection Agency and the Committees on Biomedical Research Ethics of the Capital Region of Denmark. All participants gave signed informed consent and agreed to having their history published.

Cases were recruited from the patient research register at The Danish Research Centre for Chemical Sensitivities. Thirty-seven patients who lived in or near the Copenhagen area were contacted by telephone and invited to participate. Cases were screened by a telephone interview and selected according to the extended consensus criteria for MCS [6] which were applied as follows: (1) symptom duration of at least 6 months, (2) symptoms in response to at least 2 of 11 categories of chemical exposures often associated with MCS, (3) at least one CNS symptom and one symptom from another organ system, (4) a severity score ≥ 5 (on a scale from 0 to 10) on one important area of functioning, i.e., work, social or family life, (5) symptoms occurring when exposed and improving or resolving when triggering exposures are removed and (6) symptoms triggered by exposure levels that do not evoke symptoms in other individuals exposed to the same levels.

All cases received transcranial PEMF therapy at the Danish Research Centre for Chemical Sensitivities for 30 min daily on all weekdays for 8 consecutive weeks totalling 39 treatments per patient. Treatment duration was set at 8 weeks as suggested in a previous PEMF study on treatment-resistant depression [34]. PEMF was delivered by the Re5 Independent System® (model I2010, Re5 Aps, Frederiksberg, Denmark) with a pulse generator providing pulses for the applicator. The pulses alternate between +50 and −50 V and have a frequency of 55 Hz. The pulse patterns are designed to mimic the electrical fields occurring outside nerves and muscles due to the propagation of action potentials. The Re5 head applicator is worn as a helmet and consists of seven electromagnetic coils of which two coils are located over the anterior and posterior temporal region bilaterally, one coil over the upper parietal region bilaterally and one coil over the centre of the lower occipital region. The coil generates an alternating magnetic field with a calculated maximum of 1.9 mT (19G) at a distance of 0.5 cm from the coil. The magnetic fields can induce electrical fields in tissue with a magnitude of 2.2 mV/cm at a distance of 0.5 cm from each individual coil, decreasing with distance to around 30 μV/cm 10 cm from the coil [34,20].

3 Results

Table 1 and Figs. 1–3 show the baseline, post-treatment and follow-up scores on the QEESI and SCL-92 for all three cases.

Fig. 1

The scores on the Symptom Severity Scale of the Quick Environmental Exposure and Sensitivity Inventory (QEESI) at baseline (week 0), during treatment (week 1–7), post-treatment (week 8) and during follow-up (week 9–18). Data were unavailable for case 2 at week 14 and 17. Case 3 was lost to follow-up after 13 weeks.

Fig. 2

The scores on the Life Impact Scale of the Quick Environmental Exposure and Sensitivity Inventory (QEESI) at baseline (week 0), during treatment (week 1–7), post-treatment (week 8) and during follow-up (week 9–18). Data were unavailable for case 2 at week 14 and 17. Case 3 was lost to follow-up after 13 weeks.

Fig. 3

The scores on depressive symptoms of the Symptom Check List (SCL-92) at baseline (week 0), during treatment (week 1–7), post-treatment (week 8) and during follow-up (week 9–18). Data were unavailable for case 2 at week 14 and 17. Case 3 was lost to follow-up after 13 weeks.

4 Discussion

This report describes three cases of MCS with considerable functional impairments who received PEMF therapy for 8 weeks. In a Danish MCS patient sample the median scores of the CIS, LIS and SSS of QEESI were found to be 82, 65, and 47, respectively [37]. At baseline, all three cases were above the patient sample median on the LIS which was intentional and due to case selection on the basis of severity. This also explains why the baseline scores on the other scales of QEESI were above the patient sample median as symptom severity and functional impairment are closely linked. The mean score of depressive symptoms using SCL-92 in the Danish MCS patient sample was 0.88 [37], so at baseline the degree of depressive symptoms was unexpectedly above average in two of the cases. Two out of three cases showed 35–60% improvement on all QEESI scales. The improvement in functional impairments was also reflected in reduced scores on the SDS at post-treatment. One case also experienced a 40% decrease on depressive symptoms, which is in accordance with a positive effect of PEMF on refractory depression in a previous study [34]. PEMF has been shown to activate intracellular signalling, and to promote angiogenesis and vasodilatation [20,24,35]. Although speculative, the observed effect of PEMF therapy on MCS may stem from an activation of the inhibitory brain circuits in odour processing regions, which previous studies have suggested to be hypoactive [11,12]. However, there are several limitations of this case study. A placebo effect, as well as the attention given to the participants during treatment, or the natural fluctuations of the condition cannot be ruled out as explanations for the positive effect observed in two of the cases. Further studies are needed to determine this. Interestingly, an improvement in MCS-related measures was associated with a reduced mean area of capsaicin-induced secondary punctate hyperalgesia at post-treatment, which is in keeping with the hypothesis of neural sensitization.

One of the two cases who benefited from PEMF therapy, showed partial regression of MCS at 18-week follow-up. In line with this, regression after the end of treatment has also been observed with ECT for MCS and chronic pain disorders, where maintenance treatment was attempted with success [19,41]. Similarly, maintenance treatment with PEMF therapy may also be necessary to prevent relapse of illness.

Total remission of MCS was not achieved with PEMF therapy within the present time frame. However, since the observed effect did not reach a plateau at post-treatment, an additional treatment effect may be obtained by prolonging the duration of treatment in weeks and/or intensifying the treatment by increasing the number of doses per day. When considering a new treatment, the effect of treatment should always be weighed against its adverse effects. With this aspect in mind, PEMF therapy was well tolerated by the three cases and only few and mild adverse effects were reported which is in accordance with previous studies [33,34,36]. Although one of the cases was diagnosed with depression during the intervention, we find it unlikely that the depression was related to PEMF. The depression coincided with several stressful events in the participant’s life which were reflected in a high depressive score even at baseline and these events were more likely to be the cause.

5 Conclusion

This case report indicates a beneficial effect of PEMF therapy for MCS.

6 Implication

The therapeutic effect of transcranially applied PEMF in MCS needs to be investigated by a randomized placebo-controlled trial.

Highlights

• Pulsed electromagnetic fields applied transcranially in 3 cases with multiple chemical sensitivity.

• Symptoms and functional impairments improved in 2 of 3 cases.

• Capsaicin-induced secondary hyperalgesia was reduced in 2 of 3 cases.

• Pulsed electromagnetic fields applied transcranially was a feasible treatment modality in all 3 cases with multiple chemical sensitivity.