Introduction

Anosmia represents the complete loss of the sense of smell and affects children across various age groups, presenting with distinct clinical manifestations and challenges.¹ The condition occurs in approximately 1 in 10,000 individuals, though this prevalence likely underrepresents the true occurrence in pediatric populations due to underdiagnosis and delayed recognition.² Children with anosmia face unique diagnostic hurdles because they often cannot recognise their smell deficit until social situations reveal the impairment.^2,3 Healthcare providers encounter specific challenges when evaluating pediatric anosmia due to limited standardised testing protocols and the need for age-appropriate assessment tools.⁴

Aetiology and classification

Congenital anosmia

Congenital anosmia manifests from birth and stems from developmental abnormalities in the olfactory system.⁵ Isolated congenital anosmia occurs without other associated conditions and typically results from aplasia or hypoplasia of the olfactory bulb and tract.^2,6 Children with this condition show no recollection of ever possessing smell function, and often present when family members or teachers notice their inability to detect odours.⁶

Syndromic anosmia

Several genetic syndromes include anosmia as a primary feature. CHARGE syndrome combines coloboma, heart defects, choanal atresia, growth retardation, genital abnormalities, and ear abnormalities with anosmia occurring in affected individuals.^7,8 Kallmann syndrome presents with hypogonadotropic hypogonadism and anosmia due to defective gonadotropin-releasing hormone neuron migration.^9,10 These conditions require a comprehensive evaluation beyond olfactory assessment.

Acquired anosmia

Acquired anosmia develops after birth through various mechanisms. Rhinologic disease represents the most common cause, including chronic rhinosinusitis and nasal anatomic lesions.⁵ Post-infectious anosmia follows upper respiratory tract infections, with COVID-19 creating a notable increase in pediatric cases, showing 12.5% prevalence in children aged 10-18 years.¹⁰ Traumatic anosmia results from head injuries affecting the olfactory pathways.⁴

Clinical presentation and symptoms

Children with anosmia show diverse symptoms beyond smell loss. Complete inability to detect odours characterises true anosmia, while some children may retain partial function.¹ Associated taste dysfunction occurs in many cases because flavour perception depends heavily on olfactory input.¹¹ Children often report food tastes bland or different, leading to altered eating behaviours and preferences.¹

Safety concerns emerge as significant clinical issues. Children cannot detect smoke, gas leaks, or spoiled food, creating potential hazards in daily life.² Parents frequently notice children consuming rancid milk or failing to respond to warning odours that would alert others to danger.²

Eating behaviours show notable changes in affected children. Approximately 16% of children with olfactory disorders develop picky eating patterns or anorectic traits. These behavioural changes can impact nutrition and growth, requiring careful monitoring and intervention.¹

Diagnostic challenges

Age-related testing limitations

Olfactory testing in children presents unique challenges related to developmental factors. Children under 4 years cannot reliably perform standard olfactory tests, limiting diagnostic options in very young patients. The U-Sniff test demonstrates reliability and validity starting at age 4 years, with sensitivity ranging from 79-93% and specificity of 88-95% for distinguishing normal function from anosmia.¹²

Attention span and cognitive development influence test performance. Picture identification tasks and concentration testing correlate with odour identification scores, indicating that cognitive abilities impact assessment outcomes.¹² Test administrators must account for these developmental factors when interpreting results.

Cultural and environmental factors

Odorant familiarity affects test performance across different populations. Brazilian validation of the Pediatric Smell Wheel required the substitution of three odours because children could not identify banana, cherry, and chocolate reliably.¹³ This finding highlights the need for culturally appropriate testing materials in diverse populations.

Late recognition and diagnosis

Congenital anosmia diagnosis often occurs years after the condition begins affecting daily life. One study showed diagnosis delays of up to 13 years from initial parental concerns due to the subtle nature of the condition.² Children adapt to their smell deficit and may not report symptoms until specific situations reveal the impairment.

Diagnostic considerations

Clinical history and physical examination

Comprehensive history taking focuses on the timing of smell loss onset, associated symptoms, and family history. Healthcare providers should inquire about developmental milestones, particularly regarding puberty, as delayed sexual development may indicate syndromic causes. Physical examination includes nasal endoscopy to identify structural abnormalities and evaluation for dysmorphic features suggesting genetic syndromes.⁵

Olfactory testing protocols

Standardised olfactory testing provides an objective assessment of smell function. The Sniffin' Sticks test battery evaluates threshold, discrimination, and identification components. Normative data for children aged 6-17 years establishes age-specific cutoff values using the 10th percentile to distinguish normal function from impairment.³

Age-specific considerations include modified testing approaches for younger children. The U-Sniff test uses picture-based responses suitable for children aged 3-6 years. Test-retest reliability reaches acceptable levels (r = 0.75) for clinical use in this age group.¹²

Neuroimaging studies

Magnetic resonance imaging (MRI) plays a crucial role in evaluating pediatric anosmia. MRI demonstrates higher utility than computed tomography (CT) for identifying olfactory system abnormalities.⁵ Olfactory bulb and tract evaluation reveals aplasia or hypoplasia in most cases of congenital anosmia.

Specific imaging findings include absent or reduced olfactory bulb volumes in 68-84% of congenital cases, with hypoplasia occurring in 16-32% of affected children.¹⁴ MRI also identifies associated brain abnormalities and helps distinguish congenital from acquired causes.

Laboratory and genetic testing

Endocrine evaluation becomes necessary when anosmia occurs with delayed puberty or growth abnormalities. Hormone testing includes luteinizing hormone, follicle-stimulating hormone, and growth hormone assessments.¹⁵ Genetic testing may identify specific syndromic causes such as CHARGE syndrome or Kallmann syndrome mutations.⁸

Impact on quality of life

Nutritional and feeding issues

Anosmia significantly affects eating behaviours and nutritional status in children. Reduced food enjoyment leads to decreased appetite and altered food preferences.¹ Some children develop restrictive eating patterns that require nutritional intervention and monitoring.¹

Parents report concerns about adequate nutrition when children show limited interest in meals. The condition may contribute to feeding difficulties and weight management challenges, particularly in younger children who rely on smell cues for appetite regulation.¹

Psychosocial effects

Children with anosmia experience social isolation and emotional difficulties related to their condition. Quality of life studies demonstrate reduced scores in social functioning, vitality, and mental health compared to children with normal smell function.^13,16 Depression occurs more frequently in individuals with smell disorders, affecting approximately 25-33% of patients.¹⁶

School-age children may feel different from their peers during shared meals or activities involving scent identification. These experiences can contribute to social withdrawal and reduced participation in group activities.¹³

Safety considerations

Inability to detect warning odours creates ongoing safety risks for children with anosmia. Parents must implement additional safety measures, including smoke detectors, gas leak detectors, and careful food storage monitoring.^2,15 Education about these risks becomes essential for families managing pediatric anosmia.¹⁵

Treatment approaches

Medical management

Treatment options remain limited for most causes of pediatric anosmia. Inflammatory conditions respond to topical corticosteroids, which reduce underlying inflammation and may improve olfactory function. Systemic corticosteroids provide short-term benefits for confirmed inflammatory causes but require careful monitoring in pediatric patients.¹⁷

Other medical interventions show variable success rates. Olfactory training represents the primary evidence-based treatment for non-inflammatory causes.¹⁷ This approach involves regular exposure to specific odours twice daily for extended periods.

Olfactory training protocols

Olfactory training uses systematic odour exposure to potentially improve smell function through neuroplasticity mechanisms. Standard protocols involve sniffing four different odours for 20-30 seconds twice daily over 3-6 months. Studies demonstrate clinically significant improvements in some patients with post-viral olfactory dysfunction.¹⁷

Pediatric applications of olfactory training require adaptation for age-appropriate implementation. Parents must supervise training sessions and maintain consistent schedules for optimal outcomes. Limited studies exist specifically evaluating olfactory training effectiveness in children.

Supportive care and counselling

Family education and counselling provide essential support for children with anosmia. Healthcare providers should discuss safety precautions, nutritional considerations, and psychosocial impacts with families.¹⁵ Regular follow-up appointments monitor growth, development, and adaptation to the condition.¹

Psychological support may benefit children experiencing social difficulties or depression related to their anosmia. Counselling services help children develop coping strategies and address emotional challenges associated with the condition.^13,16

Future directions and research needs

Current research focuses on developing better diagnostic tools and treatment options for pediatric anosmia. Studies investigating regenerative therapies and novel pharmaceutical interventions may provide new avenues for treatment. Improved understanding of olfactory system development could lead to preventive strategies for certain causes of congenital anosmia.⁴

Long-term outcome studies are necessary to understand the natural history of pediatric anosmia and the factors influencing recovery potential.⁴ Research into quality of life interventions and support strategies could improve care for affected children and families.¹⁶

Summary

The diagnosis and management that are currently available for children with anosmia require various approaches. This highlights the complexity and challenges these children and their families face. Early recognition through appropriate screening and testing enables timely intervention and support. Healthcare providers must maintain awareness of the condition's diverse presentations and impacts on child development, nutrition, and quality of life. Continued research efforts aim to improve diagnostic capabilities and develop effective treatments for this underrecognised condition affecting pediatric populations.